Founded in 1959, National Semiconductor has come a long way from the production of the first discrete transistors to the most complex components of modern information devices. With the ability to create devices with a level of integration from basic building blocks and single-chip systems to high-performance multi-chip and multi-functional kits, and combining analog and digital technology, the company provides optimal solutions for the consumer and communications markets in a wide range of products. Note also the basic elements of analog electronics developed and manufactured by National Semiconductor, in particular, integrated operational amplifiers, which are much less popular in Russia than, for example, Analog Devices products, although in most cases they are in no way inferior to the latter. at a significantly lower price. Operational amplifiers (op-amps) of National Semiconductor can be conditionally divided into several families (groups) according to a number of parameters, this division is partially manifested in the chip marking system used by the company. This:
1. Amplifiers for general use (General Purpose - LM).
2. High-speed (High Speed - LMH) - the unity gain frequency is more than 50 MHz.
3. Low power (Low Power - LP, LPV) - current consumption is less than 1.5 mA.
4. Micropower (Micro Power - LP, LPV) - current consumption is less than 25 μA.
5. Low Voltage (LMV) - supply voltage less than 3 V.
6. Precision - gain more than 100 dB, offset voltage less than 1 mV.
7. Low noise (Low Noise) - noise voltage is less than 10 nVC Hz.
8. Powerful (High Output Power) - the output current is more than 100 mA.
9. With input and output voltage close to the supply voltage (IO Rail to Rail).
This division, for obvious reasons, is not strict, the letter classification is also not always observed, the op-amp can be simultaneously fast, low-noise, with an output voltage close to the supply voltage, etc. In addition, microcircuits of the same type are produced in various packages and versions - for general use (commercial), for industrial use (industrial) and for special, read - military use (military), which differ in a number of parameters, in particular, in the operating temperature range . It should also be noted that along with mastering the production of new products, the company is continuously engaged in the improvement and development of previously produced products, which is clearly seen, for example, in the well-known inexpensive and very popular family of low-power op-amps LM321/358/324(single/dual/quadruple) with a current consumption of 0.2 - 0.4 mA per channel. A number of their modifications are produced: LP324/LP2902- quad micropower with a consumption current of 21 μA, LMV321/358/324 - low-voltage, with a supply voltage of 2.7 V to 5.5 V, LPV321/358/324, manufactured using proprietary BICMOS technology - micropower low-voltage with a current consumption of 9 μA, etc.
Continuing our consideration of low- and micropower op amps by National Semiconductor, let's move on to describing the latest developments of the company.
Amplifier LM7301, produced in a miniature SOT23-5 package, occupying 2 times less area than SOIC-8, designed for unipolar power supply in the voltage range from 1.8 V to 32 V at a current consumption of 0.6 mA. It has a "super" Rail to Rail input (-0.25V to +5.25V at +5V supply voltage) and a Rail to Rail output and is perfect for use in all kinds of portable equipment, modems, PCMCIA cards of laptop PCs. etc.
Amplifiers LMV751 and family LMV821/2/4(single/dual/quad) designed for use in portable RF equipment, laptop PCs, etc. LMV751 is a precision low-noise op-amp (noise level 6.5 nV / Hz Hz) with a unity gain frequency of 5 MHz and a small offset voltage of 1 mV. Operates with a single supply of 2.7 to 5.5 V and consumes a current of 0.6 mA. LMV821 at the same supply voltage, it consumes 0.3 mA per channel, the unity gain frequency is 6.5 MHz, but it has more noise, voltage and bias current. Single amplifiers are available in miniature SOT23-5 packages.
LMV771- low-noise, inexpensive precision op-amp with an extended operating temperature range from -40 to +125 °C. Operates with a single supply voltage of 2.7 to 5.5 V and consumes 0.6 mA current, providing a gain of 100 dB at a noise level of 9 nVnV / Hz Hz. The amplifier has a small bias voltage of 0.85 mV, and its temperature drift is also normalized over the entire temperature range of 0.35 μV / ° C. Allows common-mode input from 0 V. Unity gain frequency is 3.5 MHz. Produced in a miniature case SC70-5 sized 2x2x1 mm.
Amplifier Series LM6132-42 Designed for use in high-speed battery powered devices. LM6132/4(Dual/Quad) - A self-corrected, single-supply op amp that achieves an excellent slew-rate-to-power ratio. The advantage of the microcircuit is also a wide range of supply voltages from 2.7 V to 24 V, Rail to Rail input and output, and a high common-mode rejection ratio. At a unity gain frequency of 10 MHz, the current consumption is only 360 μA, which makes this op amp indispensable in portable devices such as instrumentation amplifiers, radio receivers and transmitters, display drivers, etc. LM6142/4- similar LM6132/4, but operates over a wider supply voltage range from 1.8 V to 24 V, has a higher gain of 108 dB and a common mode rejection ratio of 107 dB, a unity gain frequency of 17 MHz at a current consumption of 650 μA. They are available in SOIC and MDIP packages, as well as in CDIP packages with an operating temperature range of -55 to 125 °C.
Super-low voltage op amps are of interest LMV931/2/4(single/dual/quadruple), operating at supply voltages from 1.5 to 5.5 V, focused on use in devices powered by a single Li-Ion element. Thanks to the use of miniature cases, op amps are easily integrated into mobile phones and computer boards. The amplifiers have Rail to Rail input and output, low current consumption of 100 µA per channel, and provide a unity gain frequency of 1.4 MHz. Gain at zero frequency without feedback 101 dB. Adjusted for stable operation at any gain, as well as capacitive loads up to 1000 pF. They work in the temperature range from -40 to +125 °C. Single op amps are available in miniature SC70-5 and SOT23-5 packages, dual op amps in MSOP-8 and SOIC-8 packages, and quad op amps in TSSOP-14 and SOIC-14 packages.
Series Amplifiers LMC, manufactured using CMOS technology, also belong to the category of low- and micropower. Their characteristic feature is negligibly small input currents and, accordingly, they work in electrometric devices, devices for measuring leakage currents, various scientific equipment, etc. For example, for a precision amplifier LMC6001 typical value of input current 25 fA (f - femto 10 -15). Noteworthy is the technique used by the company to test newly manufactured amplifiers - 3 times in a row in the first minute; instruments showing an input current greater than 25 fA are rejected. This amplifier has a very low noise level of 25nV/CHz. There is protection against electrostatic potential up to 2000 V. Is issued in the MDIP case.
The range of amplifiers of the LMC series is quite wide. Low Power Amplifiers LMC6022/4(dual/quad) are made using the proprietary Double-Poly Silicon-Gate process and can operate on single- and dual-pole power supplies up to 15 V. They have a Rail to Rail output and low power consumption of 40 μA per channel. Faster Amplifiers with Rail to Rail Output LMC6032/4 at a very low price they have a very high gain of 126 dB. With a current consumption of 0.4 mA, the unity gain frequency is 1.4 MHz, and the output voltage slew rate is 1.1 V/µs. Low voltage op amps LMC6035/6 Rail to Rail outputs can operate on a single 2.7V supply (e.g. 3x NiCd batteries), making them very suitable for self-powered portable systems. Otherwise, their parameters are similar to LMC6022/4. Amplifiers are available in various packages.
Micro power amplifiers LMC6041/2/4 with a current consumption of 14 μA per channel have a record low input current of 2 fA, Rail to Rail output and can operate with a single supply from 4.5 to 15.5 V, while providing an output current of up to 21 mA. These amplifiers work great in power control systems, radiation detectors, various scientific equipment.
Precision amplifiers have similar energy parameters LMC6061/2/4, which, with a low offset voltage of 100 µV and a high gain of 140 dB, are well suited for use in self-powered instrumentation amplifiers, medical and scientific equipment. Note that the single (LMC6061) and dual (LMC6062) amplifiers of this series are also available in CDIP packages, while the operating temperature range is -55 - +125 °C.
Faster precision op amps LMC6081/2/4 at a unity gain frequency of 1.3 MHz and an output voltage slew rate of 1.5 V/μs, they consume a current of 0.45 mA from a unipolar power supply with a voltage of 4.5 to 16 V. They also have a high gain of 130dB and a low offset voltage of 150uV. The amplifiers are available in SOIC and MDIP packages.
Low power op amps LMC6482/4(Dual/Quad) - Class-typical Rail to Rail input and output amplifiers. They operate in the supply voltage range from 3 to 15 V, consuming a current of 0.5 mA per channel and provide an output current of up to 30 mA. Designed for use in various equipment with low power consumption. Currently, a single op-amp is being produced LMC7101 in SOT-23 package with parameters similar to LMC6482, and its improved version LMC8101 in microSMD and miniSOIC packages. The latter has a blocking mode (Shutdown) with an on-time of 10 μs, the current consumption in which does not exceed 1 μA.
LMC6462/4- micro power version LMC6482/4 with a current consumption of 0.02 mA. Currently, a single op-amp is being produced LMC7111 in SOT-23-5 package with parameters similar to LMC6462.
Amplifiers LMC6492/4(double/quadruple) with an extended temperature range of -55 to +125 °C are used in automotive electronics. Their parameters are basically the same as for LMC6482/4. Available in SOIC package.
Amplifiers LMC6572/4(dual/quad), designed to operate in digital devices with low supply voltage and provide a combination of very high parameters - input current of 20 fA and gain of 120 dB with a power consumption of 40 μA per channel and a power supply from a 2.7 V source. Rail exit and are available in MSOP cases.
Concluding the section of low- and micropower amplifiers, let's consider a super-economical dual op-amp with a current consumption of less than 1 μA per channel LMC6442. It is corrected for devices with a gain of more than 2 (less than -1) and is intended for use in a wide class of equipment with ultra-low power consumption - mobile phones and pagers, control sensors, scientific instruments, etc. Works with unipolar power supply from 1.8 to 11 V. Available in MSOP-8 and other packages.
The dual operational amplifier deserves special consideration. LM833 specially designed for use in high quality audio equipment. It has an extremely wide dynamic range of over 140 dB at 4.5 nV/C Hz and an extremely low THD of 0.002%. The amplifier is corrected for any gain and is ideal for all kinds of Hi-Fi - Hi-End equipment. Available in 8-pin SOIC and MDIP packages.
Let's move on to a review of National Semiconductor's high-speed op-amps. It must be said that the company has achieved very high results in their development and production, and in many respects they are superior to similar products from other manufacturers. Note that at present there are two types of high-speed operational amplifiers - along with op-amps built according to traditional circuitry using Voltage Feedback Amplifiers (VFA), amplifiers with input stages - current amplifiers with mutual couplings are widely used. These amplifiers are called "current feedback amplifiers - Current Feedback Amplifiers (CFA)". The main transfer parameter of such amplifiers is a coefficient that has the dimension of Transimpedance resistance, and the scope is all kinds of pulse amplifiers and video amplifiers for which the giant input resistance of traditional op amps is not in demand, and the maximum output voltage slew rate and unity gain frequency come to the fore, the values of which for CFA are significantly superior to the corresponding parameters for VFA.
We'll start with op amps using conventional VFA circuitry. Family LMH6645/6/7(single/dual/single with blocking) - low-voltage, low-power, high-speed Rail to Rail amplifiers with a current consumption of 650 μA per channel. In blocking mode (LMH6647), the current consumption is reduced to 50 µA. Unity gain frequency 55 MHz, slew rate 22 V/µs, typical output current 20 mA. These are typical modern amplifiers in their class, suitable for use in many electronic devices.
Amplifiers LM6152/4, continuing the series LM6132-42, designed for use in high-speed battery-operated devices. With a current consumption of 1.4 mA, the unity gain frequency is 75 MHz, and the output voltage slew rate is 30 V/µs
Higher parameters have op amps LMH6642-55- relatively inexpensive high-speed modern Rail to Rail operational amplifiers with a good ratio of performance / power consumption. They work with single- and dual-pole power supply up to 12 V.
Amplifiers LMH6642/3/4(single / dual / quad) - these are modern high-speed op-amps with parameters typical for their class. Current consumption 2.7 mA per channel, unity gain 130 MHz, slew rate 130 V/µs, typical output current 115 mA. Fast settling times and low distortion, effective short circuit protection, Rail to Rail input and output, and balancing pins make these ICs ideal for use in many modern electronic devices. Available in SOIC, miniSOIC and SOT-23 packages. Can be used as a replacement LM6152/4.
The wideband (190 MHz, 170 V/µs) Rail to Rail single-supply amplifier LMH6639 is capable of delivering 190 mA of output current. There is a Shutdown mode with an on-time of 85 ns, in which the current consumption is reduced to 400 μA. Combined with a fast settling time of 33 ns, this amplifier is well suited for use in multiplexed applications, as a buffer amplifier, CD ROM drives, etc.
Noteworthy high-speed dual amplifier LMH6672 with a maximum output current of 600 mA. The amplifier is corrected for a gain of 2 or more, providing a bandwidth of 130 MHz and a slew rate of 160 V/µs. Supply voltage range from 5 to 12 V, current consumption 6.2 mA per channel. The op-amp has a low noise level, balancing is provided. Available in SOIC, PSOP and LLP packages. It is intended for use as a main amplifier, as well as in modems and similar devices. Can be used to replace LM6181/2, LM7171 and LM7372.
Amplifiers LMH6654/5(single/dual) higher bandwidth. Current consumption 4.5 mA per channel, unity gain frequency 250 MHz, slew rate 200 V/µs, typical output current 180 mA. They have a low input noise level of 4.5 nV and 1.7 pA, a fast output voltage settling time of 25 ns and can be used in various devices. Available in SOIC-8, SOT23-5 (LMH6654) and MSOP-8 (LMH6655) packages.
Amplifiers LMH6657/8 And LMH6682/3- relatively inexpensive ultra-high-speed op amps with unipolar power supply from 3 to 12 V. They are produced using VIPTM10 proprietary technology. They are convenient for use in video signal processing devices and CD/DVD servo drives, as they have a short settling time and do not allow output voltage phase inversion when the input voltage exceeds the allowable values (LMH6682/3), which can significantly simplify the circuitry of such devices.
Amplifiers LMH6657/8(single/dual) are corrected for unity gain operation while providing 270 MHz bandwidth and 700 V/µs slew rate. Current consumption 6.2 mA per channel, output current +80/-90 mA.
Amplifiers LMH6682/3(dual/triple), provide a slew rate of 940 V/µs at a bandwidth of 190 MHz. It should be noted that these amplifiers have very low distortion coefficients of the "differential phase" type - 0.08% and "differential gain" - 0.01 dB, which is very important for high-end video equipment. Are issued in various cases.
Ultra-fast amplifiers with an output voltage slew rate of more than 1000 V/µs are designed for operation in various video devices. In the LM series, this LM6171/2 And LM6181/2(single/double), manufactured using proprietary VIPTM11 technology. The first of them is made according to VFA circuitry and provides, with a current consumption of only 2.5 mA, an output voltage slew rate of 3600 V/μs at a unity gain frequency of 100 MHz. LM6181/2 It is made according to CFA current feedback circuitry and provides an output voltage of +10 V at a load resistance of 100 Ohms. The output voltage slew rate is 2000 V/µs at a unity gain frequency of 100 MHz. The described amplifiers, despite the fact that they belong to the category "with a powerful output" - High Output - the maximum value of the output current reaches 130 mA, have very low distortions such as "differential gain" and "differential phase" and can be used in video equipment of NTSC and PAL standards , high-pass filters, etc. They are also available in SOIC and MDIP packages.
Amplifier LMH6609 designed for use in analog converters and filters. At a unity gain frequency of 900 MHz and a slew rate of 1400 V/µs, it draws 7 mA from a single-ended 10 V power supply. The amplifier is fully corrected, has a very low noise level of 3.1 nV / C Hz and a large output current of 90 mA. Available in 8-pin SOIC and 5-pin SOT packages.
Very low noise and high operating frequencies have amplifiers LMH6622-28. For the LMH6624, this parameter is 0.92 nV / C Hz and 2.3 pA / C Hz, and the unity gain frequency is 1500 MHz. The amplifier is corrected for use in devices with a gain of 10 or more and is intended for use in communications technology and medical equipment. Low noise and errors are characteristic of a dual wideband amplifier LMH6628, in which the relative level of the 2nd / 3rd harmonic at a frequency of 10 MHz is -65 / -74 dB, respectively, and the output voltage setting time with an accuracy of 0.1% is 12 ns. This makes this amplifier indispensable in the development of high-speed analog converters and input-output devices.
The amplifier is designed for use in portable video equipment and PC video cards. LM7121, produced in the SOT23-5 package. The amplifier parameters are very high: the unity gain frequency is 175 MHz, the output voltage slew rate is 1300 V/µs. It can work both with unipolar +5V supply and bipolar in the range from +5V to +15V.
Ultra-fast operational amplifiers have record parameters LM7171(single) and LM7372(double). Based on voltage feedback circuitry, they have the characteristics of current feedback amplifiers - slew rate of 4100 V/µs, unity gain frequency of 200 MHz, output current of 100 mA (LM7171) and 3000 V/µs, 120 MHz , 150 mA respectively for the LM7372 with a current consumption of 6.5 mA per channel. The amplifiers are corrected for a voltage gain greater than 2. With minimum differential gain and phase distortions of 0.01% and 0.02o, these amplifiers are well suited for video, cable and optical line equipment, radio and television broadcasting applications. Are issued in various types of cases.
Super high speed op amp series LMH67xx It is made according to the VIPTM10 proprietary technological process according to CFA current feedback circuitry and is intended for use in wideband radio and television systems. We will begin our review of these microcircuits with LMH6702- low-noise (noise voltage reduced to the input 1.83 nV) op amp with a record low level of harmonic (-100 dB at 5 MHz) and intermodulation distortion, a bandwidth of 720 MHz and an output voltage slew rate of 3100 V/µs. Such high performance orients the application of the LMH6702 in high resolution systems and instrumentation. Available in SOIC and SOT-23 packages.
Amplifier family LMH6714/15/20/22(single/dual/locked/quad) with a bandwidth of 400 MHz at a gain of 2 and a slew rate of 1800 V/μs at a current consumption of 5.6 mA are intended primarily for use in video systems. The high-impedance output state of the LMH6720, switched at 7ns TTL level, is very useful for multiplexing multiple high-speed signals onto a common transmission line. The LMH6722 quad amplifier can be effectively used in multi-channel IF and high-order active filters. Are issued in various cases.
Amplifier with single supply from 4.5 to 12 V LMH6723 combines high efficiency (current consumption 1 mA) with a wide bandwidth of 370 MHz, a high slew rate of 600 V / µs and a large output current of 110 mA, which makes it indispensable for portable video devices and all kinds of self-powered converters, trunk amplifiers, portable CD-DVD players, etc. Available in SOIC and SOT23 packages.
Concluding the section, we will consider a wideband op amp LMH6732 with adjustable bandwidth from 0 to 1.5 GHz. By changing the resistance of one external resistor, you can vary the current consumption by more than 10 times, as well as put the microcircuit into standby mode with a current consumption of 1 μA. The parameters of the microcircuit are unique for all values of the consumed current: frequency band 55 MHz, output voltage slew rate 400 V/µs, output current 9 mA at a current consumption of 1 mA and 540 MHz, 2700 V/µs and 115 mA respectively at a current consumption of 9 mA. The amplifier is capable of operating with single- and bipolar power supplies ranging from 9 to 12 V. The scope of intended applications is extremely wide - video equipment, battery-powered systems, switching devices, etc. Note that in order to reduce the design time for devices with LMH6732 National Semiconductor offers a demo board for it.
Thus, a wide range of National Semiconductor integrated operational amplifiers and their low cost make them very attractive for a wide range of Russian electronics developers. More technical information can be found on the company's website http://www.national.com.
| Execution | Frame | Temperature range | Supply voltage range | Current consumption per channel | Output current | Input and output type | Input current | Bias voltage | Bias Voltage Temperature Coefficient | Gain | Common mode rejection ratio | Coefficient of Influence of Power Supply Instability | Unity gain frequency. | Growth rate. | Noise voltage | ||||
| supply voltage | I quit | I out | In - Out | I bias | U offset | Drift | A vo | CMRR | PSRR | b.w. | SR | e noise | |||||||
| Single | Doble | Quad (quadruple) | package | IN | mA | mA | R to R | on the | mV | µV/C | dB | dB | dB | MHz | V/µs | nV/C Hz | |||
| min | Max | Max | Max | type | type | Max | type | type | type | type | type | type | type | ||||||
| LP324 | SO, TSSOP, MDIP | C | ±1.5; +3.0 | ±16.0; +32 | 0,021 | 4,0 | out | 2,0 | 2,0 | 9,0 | - | 100 | 90 | 90 | 0,10 | 0,05 | 80 | ||
| LP2902 | SO, MDIP | I | ±1.5; +3.0 | ±13.0; +26 | 0,021 | 4,0 | out | 2,0 | 2,0 | 10 | - | 97 | 90 | 90 | 0,10 | 0,05 | 80 | ||
| LMV321 | LMV358 | LMV324 | SO, MSO, TSSOP, SC-70, SO-23 | I | +2,7 | +5,5 | 0,13 | 60 | out | 11 | 1,7 | 7,0 | 5,0 | 100 | 65 | 60 | 1,0 | 1,0 | 39 |
| LPV321 | LPV358 | LPV324 | SO, MSO, TSSOP, SC-70, SO-23 | I | +2,7 | +5,0 | 0,0090 | 17 | out | 1,7 | 1,2 | 7,0 | 2,0 | 100 | 70 | 65 | 0,15 | 0,10 | - |
| LM7301 | SO, SOT-23 | I | ±0.9; +1.8 | ±16; +32 | 0,6 | 9,5 | in and out | 90 | 0,03 | 6,0 | 2,0 | 97 | 90 | 104 | 4,0 | 1,25 | 36 | ||
| LMV821 | LMV822 | LMV824 | SO, MSO, TSSOP, SC-70, SO-23 | Ext I | +2,5 | +5,5 | 0,30 | 40 | out | 30 | 1,0 | 3,5 | 1,0 | 100 | 85 | 85 | 6,5 | 2,0 | 24 |
| LMV931 | LMV932 | LMV934 | SO, MSO, TSSOP, SC-70, SO-23 | Ext I | +1,5 | +5,5 | 0,16 | 75 | in and out | 15 | 1,0 | 6,0 | 2,0 | 100 | 78 | 100 | 1,0 | 0,45 | 45 |
| LMV771 | SC-70 | Ext I | ±1.5; +2.5 | ±3.0; +6.0 | 0,60 | 66 | out | 0,000100 | 0,3 | 1,0 | 0,35 | 100 | 90 | 90 | 3,5 | 1,4 | 9,0 | ||
| LMV751 | SOT-23 | I | +2,7 | +5,5 | 0,60 | 15 | out | 0,001500 | 0,05 | 1,0 | - | 120 | 100 | 107 | 5,0 | 2,3 | 6,5 | ||
| LMC6001 | MDIP | I | ±2.3; +4.5 | ±7.7; +16 | 0,45 | 21 | out | 0,000010 | 0,35 | 1,00 | 2,5 | 123 | 83 | 83 | 1,3 | 1,5 | 22 | ||
| LMC6022 | LMC6024 | SO | I | ±2.3; +4.5 | ±8.0; +16 | 0,04 | 40 | out | 0,000040 | 1,0 | 9,0 | 2,5 | 120 | 83 | 83 | 0,35 | 0,11 | 42 | |
| LMC6032 | LMC6034 | SO, MDIP | I | ±2.3; +4.5 | ±8.0; +16 | 0,38 | 40 | out | 0,000040 | 1,0 | 9,0 | 2,3 | 126 | 83 | 83 | 1,4 | 1,1 | 22 | |
| LMC6035 | LMC6036 | SO, TSSOP | I | +2,7 | +16 | 0,40 | 5,0 | out | 0,000020 | 0,50 | 5,0 | 2,3 | 126 | 96 | 93 | 1,4 | 1,5 | 27 | |
| LMC6041 | LMC6042 | LMC6044 | SO, MDIP | I | +4,5 | +16 | 0,014 | 21 | out | 0,000002 | 3,0 | 6,0 | 1,3 | 120 | 75 | 75 | 0,075 | 0,020 | 83 |
| LMC6061 | LMC6062 | LMC6064 | SO, CDIP | I, M | +4,5 | +16 | 0,020 | 21 | out | 0,000010 | 0,35 | 0,80 | 1,0 | 132 | 85 | 85 | 0,10 | 0,035 | 83 |
| LMC6081 | LMC6082 | LMC6084 | SO, MDIP | I | +4,5 | +16 | 0,45 | 21 | out | 0,000010 | 0,35 | 0,80 | 1,0 | 124 | 85 | 85 | 1,3 | 1,5 | 22 |
| LMC6442 | SO, MSO, MDIP | I | +1,8 | +11 | 0,0010 | 0,90 | out | 0,000005 | 3,0 | 7,0 | 0,4 | 103 | 92 | 95 | 0,010 | 0,0040 | - | ||
| LMC6462 | LMC6464 | SO, MSO, CDIP | I, M | +3,0 | +15 | 0,020 | 27 | out | 0,000015 | 0,50 | 1,5 | 1,5 | 124 | 85 | 85 | 0,050 | 0,015 | 80 | |
| LMC7111 | SOT-23,MDIP | I | +2,7 | +11 | 0,025 | 7,0 | in and out | 0,000100 | 3,0 | 7,0 | 2,0 | 112 | 85 | 85 | 0,050 | 0,027 | - | ||
| LMC6482 | LMC6484 | SO, MSO, CDIP | I, M | +3,0 | +15 | 0,50 | 30 | in and out | 0,000020 | 0,75 | 3,0 | 1,0 | 116 | 82 | 82 | 1,5 | 1,3 | 37 | |
| LMC7101 | SOT-23 | I | +2,7 | +15 | 0,50 | 24 | in and out | 0,001000 | 3,0 | 7,0 | 1,0 | 110 | 75 | 80 | 1,1 | 1,1 | 37 | ||
| LMC8101 | MSMD, MSOP | I | +2,7 | +10 | 0,70 | 49 | in and out | 0,001000 | 0,70 | 5,0 | 4,0 | 80 | 80 | 80 | 1,0 | 1,0 | 22 | ||
| LMC6492 | LMC6494 | SO | I | +5,0 | +15 | 0,50 | 22 | in and out | 0,000150 | 3,0 | 6,0 | 1,0 | 110 | 82 | 82 | 1,5 | 1,3 | 37 | |
| LMC6572 | LMC6574 | SO | I | +2,7 | +10 | 0,038 | 6,0 | out | 0,000020 | 3,0 | 7,0 | 1,5 | 120 | 75 | 75 | 0,22 | 0,09 | 36 | |
| LM833 | SO, MDIP | C | ±4.5 | ±18 | 2,5 | 40 | no | 500 | 0,30 | 5,0 | - | 110 | 100 | 100 | 15 | 7,0 | 4,5 | ||
| LM6132 | LM6134 | SO, MDIP | I | +1,8 | +24 | 0,5 | 4,3 | in and out | 110 | 2,0 | 6,0 | 5,0 | 100 | 100 | 82 | 10 | 14 | 27 | |
| LM6142 | LM6144 | SO, MDIP | I | +1,8 | +24 | 0,8 | 6,2 | in and out | 180 | 1,0 | 2,5 | 3,0 | 108 | 107 | 87 | 17 | 25 | 16 | |
| LMH6645/7 | LMH6646 | SO, SOT-23 | I | ±2.5; +3.0 | ±6.0; +12 | 0,70 | 20 | in and out | 360 | 1,0 | 4,0 | 5,0 | 87 | 77 | 83 | 55 | 22 | 17 | |
| LM6152 | LM6154 | SO, MDIP | I | +2,7 | +24 | 2,0 | 8,0 | in and out | 500 | 2,0 | 5,0 | 10 | 107 | 84 | 91 | 75 | 30 | 9,0 | |
| LMH6622 | SO, MSO | I | ±2.5 | ±6.3 | 4,3 | 90 | no | 4700 | 0,20 | 1,2 | 2,5 | 83 | 100 | 95 | 160 | 80 | 1,6 | ||
| LM6171 | LM6172 | SO, MDIP | I | ±5; +2.7 | ±16; +18 | 4,0 | 135 | no | 1000 | 3,0 | 6,0 | 6,0 | 99 | 110 | 95 | 100 | 3600 | - | |
| LM6181 | LM6182 | SO, MDIP | I | ±3.5 | ±16 | 7,5 | 130 | no | 2000 | 2,0 | 4,0 | 5,0 | - | 60 | 80 | 100 | 1400 | 4,0 | |
| LM7121 | SO, SOT-23 | I | ±5; +2.7 | ±18; +15 | 4,8 | 52 | no | 5200 | 0,90 | 8,0 | - | 72 | 93 | 70 | 175 | 1300 | 17 | ||
| LM7171 | SO, MDIP, CDIP | I, M | ±2.7 | ±18 | 6,5 | 100 | no | 2700 | 1,0 | 3,0 | 35 | 81 | 105 | 90 | 200 | 4100 | 14 | ||
| LM7372 | LLP, SO, PSOP | I | ±4.5 | ±18 | 6,5 | 150 | no | 2700 | 8,0 | 10 | 12 | 80 | 93 | 90 | 120 | 3000 | 14 | ||
| LMH6609 | SO, SOT-23 | I | ±3.0 | ±6.3 | 7,0 | 90 | no | 2000 | 0,8 | 3,5 | - | - | 73 | 73 | 180 | 1400 | 3,1 | ||
| LMH6624 | LMH6626 | SO, MSO, CDIP, SOT-23 | I, Ext I | ±2.5; +5.0 | ±6.0; +12 | 15 | 100 | no | 50 | 0,25 | 0,95 | 0,25 | 79 | 90 | 90 | 1500 | 350 | 0,92 | |
| LMH6628 | SO, MSO, CDIP, CPACK | I | ±2.5 | ±6.0 | 9,0 | 85 | no | 300 | 2,0 | 5,0 | 5,0 | 63 | 62 | 70 | 300 | 550 | 2,0 | ||
| LMH6639 | SO, MSO | I | ±2.5; +3.0 | ±6.0; +12 | 3,6 | 160 | out | 1000 | 1,0 | 7,0 | 8,0 | 100 | 93 | 96 | 190 | 170 | 6,0 | ||
| LMH6642 | LMH6643 | LMH6644 | SO, SOT-23 | I | ±2.5; +3.0 | ±6.0; +12 | 2,7 | 115 | out | 1500 | 1,0 | 7,0 | 5,0 | 80 | 72 | 75 | 130 | 130 | 17 |
| LMH6654 | LMH6655 | SO, SOT-23 | I | ±2.5; +3.0 | ±6.0; +12 | 4,5 | 180 | no | 5000 | 1,0 | 4,0 | 6,0 | 67 | 90 | 76 | 250 | 200 | 4,5 | |
| LMH6657 | LMH6658 | SO, MSO, SC-70, SOT-23 | I | ±2.5; +3.0 | ±6.0; +12 | 6,0 | 45 | no | 5000 | 1,1 | 7,0 | 2,0 | 85 | 82 | 82 | 270 | 700 | 11 | |
| LMH6672 | SO, PSOP, LLP | I | ±2.5 | ±6.5 | 6,2 | 600 | no | 8000 | 0,2 | 4,0 | - | 68 | 100 | 78 | 200 | 170 | 4,5 | ||
| LMH6682 | LMH6683* | SO, MSO, TSSOP | I | ±2.5; +3.0 | ±6.0; +12 | 6,5 | 80 | no | 5000 | 1,1 | 7,0 | 2,0 | 85 | 82 | 76 | 190 | 940 | 12 | |
| LMH6702 | SO, SOT-23 | I | ±5.0 | ±6.0 | 12 | 80 | no | 6000 | 1,0 | 6,0 | 13 | - | 52 | 48 | 720 | 3100 | 1,8 | ||
| LMH6714/20 | LMH6722 | SO, SOT-23 | I | ±5.0 | ±6.0 | 5,6 | 70 | no | 1000 | 0,2 | 6,0 | 8,0 | - | 58 | 54 | 400 | 1800 | 3,4 | |
| LMH6715 | SO, CDIP | I | ±5.0 | ±6.0 | 5,0 | 70 | no | 5000 | 2,0 | 8,0 | 30 | - | 60 | 56 | 480 | 1300 | 3,4 | ||
| LMH6723 | SO, SOT-23 | I | +4,5 | +12 | 1,0 | 110 | no | 400 | 1,0 | 3,5 | - | - | 64 | 60 | 370 | 600 | 4,3 | ||
| LMH6732 | SO, SOT-23 | I | ±4.5 | ±6.0 | 9,0 | 115 | no | 2000 | 3,0 | 8,0 | 16 | - | 62 | 52 | 540 | 2700 | 2,5 | ||
Founded in 1959, National Semiconductor has come a long way from the production of the first discrete transistors to the most complex modern microelectronic devices. One of the priority activities of the company throughout its existence was the development of integrated operational amplifiers (op-amps).
In 1968, National Semiconductor engineers created the world's first two-stage operational amplifier LM101, which marked the beginning of a whole trend in building all kinds of analog electronic devices. Modern National Semiconductor operational amplifiers correspond to, and in many respects surpass the world level of devices of this class, while having prices significantly lower than those of other companies, allowing developers to successfully solve a wide range of problems in creating various electronic equipment.
Most modern integrated operational amplifiers are made in a direct amplification circuit with differential inputs and are designed for symmetrical bipolar supply (although unipolar is increasingly used). In addition to two inputs, an output and power outputs, an operational amplifier can also have outputs for balancing, correction, programming (setting certain parameters by the amount of control current) and others.
Ideally, an op amp should have infinite voltage gain, infinite input and infinitely small output impedance, infinite output amplitude, infinite amplifying frequency range, and zero noise. The parameters of operational amplifiers should not depend on external factors, supply voltage and temperature. Under these conditions, the transfer characteristic of an operational amplifier covered by negative feedback (NFB) exactly corresponds to the transfer characteristic of the CNF circuit and does not depend on the parameters of the amplifier itself.
Real operational amplifiers have characteristics that differ from ideal ones, which is the reason for their comprehensive classification. A real operational amplifier is a compromise of mutually exclusive requirements with the achievement of the best properties in one or more parameters, which can be: minimizing the bias voltage and input currents, achieving the maximum bandwidth of amplified frequencies and the slew rate of the output voltage, reducing the consumed current and supply voltage, and others. The parameters of an operational amplifier can be divided into several groups - input, output, amplifying, frequency, energy, noise, etc.. Along with the operational parameters that determine the nominal temperature mode of operation of the operational amplifier, the permissible parameters of the input and output circuits and the requirements for power supplies, the maximum possible values of a number of parameters are also very important, the excess of which is not allowed. Currently, there is a certain (though not very strict) classification of operational amplifiers according to a combination of various parameters, reflecting their preferred use in a particular class of devices. We also note that the parameters of operational amplifiers are largely determined by their circuit design and the semiconductor technology used.
National Semiconductor uses the following classification of operational amplifiers, which is partially manifested in the first two or three letters of the marking of microcircuits manufactured by the company:
- General purpose amplifiers (General Purpose - LM, LMC) - gain up to 100 dB, bias voltage over 1 mV, unity gain frequency up to 10 MHz.
- Low-power (Low Power - LP, LPV) - current consumption is less than 1.5 mA.
- Micropower (Micro Power - LP, LPV) - current consumption is less than 25 μA.
- Low Voltage (LMV) - supply voltage less than 3 V.
- Precision (Precision - LMP) - gain more than 100 dB, offset voltage less than 1 mV.
- High-speed (High Speed - LMH) - a unity gain frequency of more than 50 MHz.
- Low noise (Low Noise) - noise voltage less than 10 nV / Hz 1/2.
- Powerful (High Output Power) - the output current is more than 100 mA.
- With output and input voltage close to the supply voltage (Rail to Rail Output/Input).
In Rail to Rail amplifiers, the maximum and minimum amplitude of the output voltage practically coincides with the corresponding values of the supply voltage, and the permissible values of the common-mode input voltage are equal to or even can go beyond the supply voltage. The latter is used, for example, in amplifiers with a unipolar supply with the possibility of applying a negative voltage to the input.
As mentioned above, for obvious reasons, this division is not strict, the letter classification is also not always observed, the operational amplifier can be simultaneously low-voltage, high-speed, low-noise, with an output voltage close to the supply voltage, etc. In addition, operational amplifiers of the same type are available in different packages, as well as two, three or four amplifiers in one package (multichannel) and, finally, in versions designed for general (Commercial - C), industrial (Industrial - I, E) and military applications (Military - M), which differ in a number of parameters, in particular, in the operating temperature range (C: 0...+70 °C; I: -40...+85 °C; E: -40... +125 °C M: -55...+125 °C).
It should also be noted that along with mastering the production of new products, the company is continuously improving and developing operational amplifiers that were produced earlier, which is clearly seen, for example, in the well-known inexpensive and very popular family of low-power quad operational amplifiers with single supply (Single Supply) LM124 / 224/324/2902 and current consumption of 0.2–0.4 mA per channel. A number of their modifications are produced: LP324/LP2902 - micropower with a current consumption of 21 μA, LMV324 - low voltage, with a supply voltage of 2.7 to 5.5 V, LPV324 - micropower low voltage with a current consumption of 9 μA, manufactured using BiCMOS proprietary technology, and other .
We also note that for modern operational amplifiers, as, indeed, for other integrated circuits, there is a tendency to reduce the size and increasingly use surface-mounted packages. The previously widespread DIP and TSSOP packages are being replaced by much smaller SOIC, SOT-23 and SC-70 (the latter measures 2x2x1mm); a number of surface-mount chips are available in especially small-sized microSMD packages with dimensions of 1.285 × 1.285 × 0.85 mm or less.
Our previous article looked at National Semiconductor's high speed op amps. Here we will focus on other types of operational amplifiers released by the company in recent years. Let's start the review with amplifiers, the main parameters of which at a supply voltage of 5 V are given in Table 1 and correspond to general-purpose operational amplifiers.
Table 1. Main parameters of modern general purpose operational amplifiers National Semiconductor
General Purpose Operational Amplifiers
As can be seen from Table 1, most of these amplifiers are low-voltage and low- and micro-power in miniature packages, which reflects modern trends in the design of electronic equipment.
The LMV341/2/4 family of operational amplifiers is designed for use in self-powered portable equipment. Operational amplifiers are characterized by very high input current and noise parameters. In Shutdown mode, current consumption is reduced to a typical value of only 45 pA, and the transition time to the operating mode does not exceed 5 µs. The amplifiers are available in various cases, including the SC70-6L, which is very suitable for placement on the motherboards of personal computers and laptops. Note that these amplifiers are operable in an extended temperature range (up to 125 °C).
A characteristic feature of the families of operational amplifiers LMV931 / 2/4 and LMV981 / 2 (with shutdown mode) is a very low minimum supply voltage of 1.8 V, and therefore they are positioned by the company for use in equipment powered by a single Li-Ion galvanic element, as well as for power control systems. These amplifiers also feature Rail to Rail input and output and a very high (101 dB) gain with a relatively low noise level, which makes it possible to use these operational amplifiers in low-voltage powered audio equipment.
The LMV321/358/324 and LPV321/358/354 op amp families (the low-voltage and micro-power versions of their respective super-popular LM series op-amps), as well as the LM2904/02 miniature microSMD and LP2902 op-amp families (analogues of the LM358/324 and LP324) are classic modern operational amplifiers of general application and can be used in a wide class of devices. Note that the LM2904/02 and LP2902 can operate on single or dual power supplies ranging from 3V to 32V.
The LMV301 op amp is a CMOS version of the LMV321. It features extremely low input current and low minimum supply voltage to amplifiers in a tiny SC70 package and can be used in sample-and-hold devices, photosensor signal amplifiers, and other battery-powered devices.
Operational amplifiers of the LMV821/22/24 family are characterized by relatively high speed (unit gain frequency 5 MHz, output voltage slew rate 1.4 V/µs) with low power consumption. They also have good parameters for bias voltage and its drift (3.5 mV and 1 µV/°C, respectively). Available in various cases and designed for use in communication technology - modems, wireless and mobile phones and other devices.
The LMC7101 rail-to-rail input/output op-amp and its micro-power variant LMC7111 are miniature CMOS op-amps designed for use in a variety of portable, self-powered applications. Due to their very low input current, they can be used in sample-and-hold devices and other devices that require a high input resistance (guaranteed value of at least 1 TΩ).
Noteworthy are the LM7301 op amps with Rail to Rail input and output, which combine very high values of various parameters, in particular, a wide supply voltage range, relatively fast response, high gain and common mode rejection, as well as CMOS op amps LMC8101 with the ability to switch off. These amplifiers are available in miniature SOT-23 and microSMD packages and can be used in various devices with appropriate parameters.
Relatively powerful and fast op-amps LM8261/2 and LM8272 with Rail to Rail input and output and unlimited load capacity are designed for use in driver circuits for LCD screens, DAC output stages, headphone amplifiers and other devices. They operate over a wide supply voltage range and are characterized by low noise and distortion levels.
Low-noise operational amplifiers of the LMV721/2 family are designed for use in the input stages of amplifying equipment, including battery-powered ones. They are available in miniature and open-frame designs for embedding in various devices, such as electret microphones.
Precision operational amplifiers
Next, we turn to the consideration of the latest developments of precision National Semiconductor operational amplifiers, the main parameters of which at a supply voltage of 5 V are given in Table 2. In addition to the parameters of general-purpose operational amplifiers for precision amplifiers, the temperature drift of the bias voltage, gain and common-mode rejection coefficients are very important. signals (Common Mode Rejection Ratio - CMRR) and the influence of supply voltage instability (Power Supply Ripple Rejection - PSRR).
Table 2. Main parameters of modern National Semiconductor precision operational amplifiers
The LMC6081/2/4 and LMC6482/4 families of op-amps with Rail to Rail input and output are based on CMOS technology and are typical precision op-amps capable of operating with a single supply. Their micropower counterparts with a current consumption of 20 μA and reduced speed are also available - LMC6061/2/4 and LMC6462/4. The scope of these operational amplifiers is instrumental amplifiers, signal processing devices, signal amplifiers for piezoelectric and radiation sensors, medical equipment (amplifiers of biopotentials), etc.
A distinctive feature of the LMC6001 operational amplifiers is a negligible typical input current value of 10 fA and, accordingly, the ability to work in electrometric devices, devices for measuring leakage currents, radiation detectors, various scientific equipment, etc. The technique used by the company to test each of the of newly manufactured LMC6001 chips - 3 times in a row in the first minute. Instances with an input current greater than 25 fA are rejected. The advantage of operational amplifiers is also a low noise level of 22 nV / Hz 1/2 and the presence of protection against electrostatic potential up to 2000 V. It is available in MDIP packages and a round MCAN glass-to-metal package. Note that the successful use of operational amplifiers with low input currents is possible only in the absence of leakage currents on the surface of the circuit board. The magnitude of these currents can exceed the input currents of the amplifier by several orders of magnitude and, therefore, cause a significant shift in its zero. The way out is to create special security rings on the printed circuit board around the inputs of operational amplifiers or connect the amplifier inputs to other circuit elements outside the board. Samples of printed circuit board patterns for mounting amplifiers with ultra-low input currents are available on the company's website.
LMV751 and LMV771/2/4 low-noise precision operational amplifiers with Rail to Rail output and unipolar power supply are available in miniature packages and are designed for use in the input stages of various equipment. They are characterized by increased speed and low distortion, which makes it possible to use these operational amplifiers in high-quality equipment with low-voltage power supply.
It should be noted that National Semiconductor produces special operational amplifiers - dual LM833 and quad LM837 (not shown in the table) - for use in Hi-Fi class audio equipment. In terms of their parameters, these amplifiers are close to precision ones and are distinguished by low offset voltage (0.3 mV), high gain (110 dB), very low noise level in the audio range (4.5 nV / Hz 1/2) and extremely small non-linear distortion (0.0015%). Operational amplifiers are corrected for any gain up to unity, and along with their use in pre-amplifiers, they can be used in a wide variety of equipment to amplify weak signals.
National Semiconductor's latest achievement is the LMP2011/2/4 series of affordable, ultra-precise op-amps, based on a unique continuous input offset correction technology, with negligible offset voltage (0.8 µV typical) and temperature drift (0.015 µV/°). FROM). Unlike other op amps that use relatively low-frequency chopper stabilization, which creates significant noise and signal distortion, the LMP201x has a correction frequency of 35 kHz, which allows the main noise spectrum to be transferred to the high frequency region, thereby achieving a very low level. noise and distortion in the frequency range up to several tens of kilohertz. In general, the combination of excellent characteristics of the LMP201x operational amplifiers, such as ultra-low offset and drift, very high bandwidth and slew rate for precision operational amplifiers, combined with low noise and low current consumption, makes it possible to use these microcircuits in a wide class of devices with improved accuracy and temperature stability.
To conclude this review of precision op amps, let's take a look at another recent National Semiconductor product, the LMP8270/1 family of precision differential amplifiers with a fixed gain and an ultra-wide input common-mode voltage range, designed for use in current-measuring devices, automotive electronics, and other circuits in which it is necessary to isolate the weak differential signal against the background of a very large common-mode voltage.
The structure and typical switching circuit of the LMP8271 amplifier in the current meter circuit are shown in fig. 1. The IC contains a proprietary level shifter input and a two-stage amplifier with a total gain of 20. The LMP8270 features no OFFSET pin. In a typical switching circuit, the connection between the stages is carried out through the simplest RC low-pass filter with an external capacitor.
Rice. 1. Structure and typical switching circuit of the LMP8271 amplifier
The LMP8270 amplifies only the positive polarity of the input signal, while the LMP8271 can also amplify the negative signal. The ability to amplify the negative input voltage V IN is achieved by shifting the output voltage level V OUT by some constant value according to the graphs shown in fig. 2. The shift is performed by applying a control voltage to a special input of the LMP8271 OFFSET chip. If the OFFSET input is connected to ground, the LMP8271 only highlights the positive input signal. When the supply voltage V S is applied to the OFFSET pin, half the supply voltage is added to the output voltage of the amplifier, and thus the amplifier input becomes bipolar. In principle, any voltage V X from 0 to V S can be applied to the OFFSET input, while V X /2 is added to the output voltage.
Rice. Fig. 2. Dependence of the input and output voltage of the LMP8271 amplifier on the control signal OFFSET
Programmable operational amplifiers
National Semiconductor produces a number of operational amplifiers, the parameters of which can be controlled by changing the current through a special pin of the microcircuit - the so-called programmable operational amplifiers. The latest model of a programmable operational amplifier - the LMV422 dual amplifier - is interesting in that it can operate in two modes, normal and economical, while, of course, the amplifier parameters deteriorate, but the main functions are preserved, which can be very useful, for example, to maintain equipment in " “standby” state, switching to backup power, etc. In normal mode (Full; the PS control pin is grounded), the operational amplifiers consume a current of 400 μA and have parameters close to precision amplifiers (see Table 1). In the economy mode (Low; more than 4.5 V is applied to the PS control pin), the current consumption is reduced to 2 μA, and the amplifier becomes ultra-micropower. Each chip amplifier has its own independent PS control pin. The LMV422 op amps are corrected for gain greater than 2 and are available in a 10-pin MSOP package.
Combined devices
The tendency to reduce the size of electronic equipment leads developers to create various combined devices based on operational amplifiers. In particular, for the needs of video equipment, National Semiconductor produces sets of high-speed operational amplifiers with LMH6570/2/4 multiplexers, the parameters of which are shown in Table 3.
Table 3. Main parameters of National Semiconductor multiplexer amplifiers
The LMH6572 chip contains three sets of 2:1 multiplexers and high-quality buffer amplifiers with a gain of 2, and LMH6570 and LMH6574 - respectively 2 and 4 buffer amplifiers, a multiplexer and a high-quality high-speed operational amplifier with very high parameters for frequency response, slew rate, non-linear distortion and noise, which allows them to be used in various video signal processing and amplification devices, monitors, multichannel ADCs, high-definition television equipment, etc. values of distortions specific for video signals such as "differential gain" and "differential phase". The structure and typical switching circuit of the LMH6570 multiplexer and the table of its states are shown in fig. 3. The operation of the multiplexer is controlled by standard logic levels on the SEL and SD pins.
Rice. 3. Structure and typical switching circuit of the LMH6570 multiplexer and its status table
Many power supplies and other applications often use op-amps in conjunction with voltage references (VREs). National Semiconductor manufactures several combo ICs containing two or more fixed or variable reference op amps. For example, consider the LM432 microcircuit, consisting of two operational amplifiers similar to the popular LM358, and a fixed 2.5 V reference voltage source with an output current of up to 10 mA and an instability of no more than 4 mV in the temperature range from 40 to +85 ° C. The structure of the microcircuit is shown in fig. 4. The range of its applications can be the most diverse - the simplest linear voltage stabilizers, PWM pulse converters, etc.
Rice. 4. The structure of the LM432 chip
Analog Comparators
National Semiconductor's product range also includes a large number of integrated analog comparators, which the company has been producing with great success for many years. In particular, the LM139/239/339 series of single-supply comparators introduced in 1970 turned out to be so successful that its modifications LM193/293/393/2903 and others are still produced by several companies in different countries.
Along with the parameters common to operational amplifiers for comparators, the switching time (Response Time) is very important - the time interval from the beginning of the comparison of input voltages to the moment when the output voltage reaches the corresponding logic level. Modern low-voltage comparators are usually made using BiCMOS technology, which allows you to combine high speed and low noise with low power consumption, as well as to obtain an output voltage close to the supply voltage. Like op amps, comparators can be broadly classified into general purpose or general purpose, high speed, micro power, rail to rail output, precision, etc., and National Semiconductor uses the same system to label them as for op amps. The main parameters of modern National Semiconductor comparators at a supply voltage of 5 V are shown in Table 4.
Table 4. Main parameters of modern National Semiconductor analog comparators
The family of universal comparators, shown in the first line of the table, is made using bipolar technology with an output in the form of an open collector (OC), is operable in a wide range of supply voltages (both bipolar and unipolar) and is compatible with various types of digital logic devices in terms of output voltage: TTL, CMOS, ECL, etc. The latest comparators of the family are made in miniature microSMD packages and are designed for use in self-powered portable devices.
The LMV331/393/339 comparators are a low-voltage version of the previous family, made using BiCMOS technology. They are positioned for use in devices with unipolar power supply from 2.7 to 5 V.
The LP339 quad micropower comparator is based on bipolar technology and is designed for use with CMOS logic devices over a wide range of supply voltages. It is noteworthy that the amount of current consumed by one comparator (15 μA) does not depend on the supply voltage.
Micropower CMOS comparators LMC7211 with push-pull output (2T) and LMC7221 with open drain (OS) output are available in miniature SOT23 packages and are designed for use in various portable devices - laptops, mobile phones, etc. LMC7215 and LMC7225 comparators with a current consumption of only 0.7 μA. These comparators have Rail to Rail input and output and are intended for use in standby circuits.
National Semiconductor's latest comparators are based on BiCMOS technology and feature a unique combination of different parameters. Modern universal LMV7235/39 comparators provide switching times of 45 ns at a current consumption of 65 µA. The high-speed version of the LMV7219 has a switching time of 7 ns, while the low-voltage versions of the LMV7271/2/5 and LMV7291 operate at a supply voltage of 1.8 V. Clear switching of the comparators when comparing slowly changing input signals is guaranteed by the internal hysteresis of the circuit. All comparators in the LMV72xx series are available in miniature packages.
The LMV761/2 precision single and dual CMOS comparators feature very low offset voltage and input current at relatively high speed. The LMV761 comparator has a Shutdown mode, which reduces the current consumption to 0.2 µA and the comparator output goes into a high-impedance state. The transition time to the operating mode does not exceed 4 μs. Note that according to the specifications for these ICs, the unused SD disable pin must not be left free, but should be connected to the positive power pin.
National Semiconductor's product portfolio includes a range of combination ICs based on analog comparators. This, for example, is the LMS33460 supply voltage drop detector, which forms an active (zero) level when the device supply voltage drops to 3 V. The structure of the LMS33460 microcircuit and a typical circuit for its inclusion are shown in fig. five.
Rice. Fig. 5. The structure of the LMS33460 supply voltage drop detector chip (a) and its typical switching circuit (b)
The LMS33460 microcircuit, made in a miniature SC70-5 package, includes a precision reference, a comparator with hysteresis, and an open-drain output stage. The input voltage range of the microcircuit is 0.8–7 V, the amount of current consumed does not exceed 1 μA, while the switching time to the active state is 70 μs.
Choosing the right op-amp
To reduce the time spent on selecting and testing operational amplifiers, National Semiconductor has created a convenient online technology, Amplifiers Made Simple, which is part of the WEBENCH software shell located on the company's website. The new interactive tool has a powerful search engine that allows you to quickly and accurately find the right component among the mass of other products, each of which has a wide variety of electrical characteristics.
At the first stage, Amplifiers Made Simple allows you to choose the optimal type of operational amplifier that meets the requirements of the user. The op amps are then searched among National Semiconductor products to find the op amps that are best suited for that particular task. Like all other tools in the WEBENCH family, Amplifiers Made Simple is completely free. Various tools of the family are integrated with each other, which creates additional convenience for the user.
With Amplifiers Made Simple, the electronics designer no longer has to do time-consuming circuit calculations and costly physical prototyping. The technology provides instant access to the latest SPICE models, parameters and other information about National Semiconductor op amps, and allows the user to compare characteristics of multiple devices simultaneously. National Semiconductor guarantees delivery of any WEBENCH-supported products within 24 hours.
The wide range and low cost of National Semiconductors integrated operational amplifiers, as well as the possibility of online selection, make them very attractive to a wide range of electronics developers. You can find information on the considered operational amplifiers, as well as other components manufactured by National Semiconductor, at http://promelec.ru/lines/nsc.html or on the manufacturer's website www.national.com.
Literature
- Volovich G. I. Circuitry of analog and analog-digital electronic devices. Moscow: Dodeka-XXI Publishing House. 2005.
- National Analog Products Databook. 2004 Edition.
- Shtrapenin G. L. High-speed operational amplifiers from National Semiconductor // Chip News. 2003. No. 10.
Op-Amp Differential Amplifier with Single Supply - Switching On
Let's start with the terms to make it clearer what will be discussed below.
An amplifier is a node or even a whole device that can increase the power of an electrical signal passing through it. The word "power" is not in vain used here, since there are other devices that increase individual current indicators - its strength or voltage (for example, transformers), such elements cannot be called amplifiers.
Differential amplifiers are a type of amplifiers in which the output signal corresponds to the potential difference at the inputs (most often there are two inputs, but differential amplifiers with one input are very rarely used, for example, repeaters) increased by a certain factor.
Op-amp (an abbreviation for the words "operational amplifier", in English it sounds like an operational amplifier or OpAmp) is a subspecies of DC differential amplifiers that have a very high gain.
They are indicated in the diagrams as follows.
Op-amp with single supply
The power supply of the op-amp can be bipolar (the power supply has an output of negative potential, positive and zero) or unipolar (only positive potential and zero are supplied).
The unipolar power supply of the op-amp is much easier to implement modern circuits powered by batteries or batteries.
The advantages of unipolar power supply of the op-amp include the following:
1. Power consumption is reduced (in comparison with bipolar ones);
2. Only one current source is required;
3. It is possible to build efficient circuits for portable devices powered by rechargeable batteries.
That is why most modern operational amplifiers are designed for unipolar supply and work in fact halfway (for example, the Rail to Rail family).
But due to the low accuracy and reduced gain, special attention must be paid to the correct selection of the op amp.
Due to the large range of op-amps and their functionality, the procedure for choosing a ready-made amplifier for your own needs becomes quite complicated. The following circuit from the leading manufacturer STMicroelectronics can help with this.
Here GBR is the cutoff frequency and Icc is the current consumption. To select ready-made elements from other manufacturers, you can use the search for direct analogues.
Inclusion of an op-amp with unipolar power supply in circuits
Below, we consider the most popular implementations of typical OS tasks.
The simplest is the inclusion of an op amp in circuits where the input signal is relative to ground.
The inverting amplifier will look like this.
The output signal will be calculated by the formula
The circuit will only work if Vin is positive.
Below is an op-amp with a bias applied to the non-inverting input.
A more powerful non-inverting op-amp will turn on like this.
Here the gain is 10 (assuming R1 is 910 kΩ, R2 is 100 kΩ, and R3 is 91 kΩ, LM358 is used as DA1). The calculation is based on the formula k=1+R1/R2.
Differential amplifier option.
15.07.2019 - 08:24
Maybe
Uout \u003d (1 + 2 R1 / R2) (Uin1 - Uin2) I wonder what the output voltage is if Uin1
Battery-powered mobile electronic systems are becoming more and more common.
Typically, they use a single supply voltage of 5 V or less. Schemes with unipolar
power supply can reduce the complexity of the power supply and often increase the cost-effectiveness
devices.
Operational amplifiers (op-amps) are predominantly used in bipolar circuits, since the input and output signals of the op-amp can most often have both positive and negative polarity relative to the common circuit bus. In the event that the non-inverting input of the op-amp is connected to a common bus, there is no common-mode input voltage that causes an error in signal conversion by the op-amp circuit (Fig. 1).
Then the output voltage of the op amp is Vout=-Vin R2/R1 .
If the input signal source is not connected to a common bus (Fig. 2, a), then the potential difference Vsf between the common bus and the output of the input signal source affects the output voltage Vout=-(Vin+Vsf)R2/R1.
Sometimes this is acceptable, but more often the output voltage of the amplifier must necessarily be determined only by the input signal Vin. In this case, the op-amp is used in a differential connection, and a bias is applied to the second input, exactly equal to Vsf (Fig. 2, b). The voltage Vsf exists in both input circuits, and, therefore,
is the in-phase input signal. The scheme of inverting connection of an op-amp with a unipolar supply is shown in fig. 3 .
Here, the input voltage is not tied to the midpoint of the power source, as is usually done in the case of a two-pole power supply of the op-amp, but to the negative pole of the power source. This circuit does not work if the input voltage is positive, because the output voltage must go negative in this case, and there is no negative power supply here. For normal operation with negative input signals in this circuit, you should use op amps that allow connection of inputs to power buses. The indispensable requirement to connect the inputs to a common bus or other reference voltage makes it difficult to build circuits on an op-amp with a unipolar supply. It is most natural to use a unipolar power supply for operational amplifiers when the input signal source is unipolar, for example, a photodiode (Fig. 4).
In other cases, various methods of biasing the input and output voltages of the op-amp can be used.
Single supply op amp bias
On fig. 5 shows three main schemes for connecting a bias source with a unipolar power supply to the op-amp.
The scheme in fig. 5a is an inverting adder,
in fig. 5, b - differential amplifier,
and in fig. 5c - non-inverting adder.
In general, the relationship between the input and output voltages in these circuits can be represented by the equation
Vout=kVin+b . (3)
Equation (3) corresponds to the graph of the static transient response of the circuit with an op amp in the form of a straight line
lines (Fig. 6).
Table 1.
In table. 1 shows the values of the constants k and b for equation (2), corresponding to the schemes in Figs. five . If in the diagram in Fig. 5, b swap the sources V IN and V OF , then the lower line in the column “Fig. 5, b" tab. one.
The circuits and values of the constants k and b are chosen so that for any possible values of the input voltage
V IN condition 0< V OUT < V S . (4)
Typically, k is determined by the required circuit gain, so the designer can only choose the circuit configuration and the constant b. In more detail, the offset of the op-amp with unipolar power is discussed in. A typical op-amp switching circuit for amplifying AC signals powered by a unipolar source is shown in fig. 7.
Here, the bias voltage is half the supply voltage. Bias divider resistors can be chosen high enough to avoid stressing the power and input signal sources.
Introduction of an artificial zero point
The use of bias circuits can be abandoned if an artificial zero (middle) point is introduced, i.e., a circuit point whose potential is located approximately in the middle between the potentials of the positive and negative poles of a unipolar power source. In order for the circuit to amplify bipolar signals, an input signal source is connected between the input of the inverting amplifier and the artificial zero point.
(Fig. 8) .
In this case, in order to avoid output voltage bias, the load R L is connected between the amplifier output and the artificial zero point. This complicates the construction of circuits that form the zero point.
On fig. 9 shows examples of zero point potential formation schemes. The simplest is a resistive voltage divider, the middle point of which is connected to an artificial zero point 0 (Fig. 9, a). However, in the presence of a load R L, the load current I L flows through one of the resistors of this divider, creating a voltage asymmetry between the poles of the power source and point 0, and the degree of this asymmetry depends on the current strength
loads. Reducing the resistance of the divider reduces the non-symmetry of these voltages, but at the same time, energy losses in the divider increase.
The circuit with a zener diode (Fig. 9, b) provides good stabilization of the potential of the artificial zero point relative to the negative pole of the power source. As a zener diode in this circuit, it is advisable to use a two-output reference voltage source (or an adjustable three-output source, such as, for example,
(TL431). This circuit works well when the op-amp is sinking output current, but keeping the 0-point potential stable with a significant sinking output current requires a low resistance resistor R, which again
causes higher losses. Similar problems arise when using a voltage stabilizer with a series control element to form an artificial zero point.
The best performance has a circuit with an operational amplifier connected according to a non-inverting follower circuit to the midpoint of a resistive voltage divider (Fig. 9, c). In this circuit, the divider can be high-resistance, since it is loaded only with the input quiescent current of the operational amplifier. The op-amp compares the potential at the output of the circuit with the potential at the midpoint of the divider and maintains the voltage at its output such that the difference between the compared potentials is zero. This effect is achieved through the action of negative feedback. At low quiescent currents consumed by this circuit (less than 1 mA), such an active divider has an output impedance of no more than 1 ohm.
Even more effective is the use of special microcircuits for the formation of an artificial zero point (Fig. 9, d). Texas Instruments (USA) produces ICs of the TLE2425 type. This IC is manufactured in a small-sized TO-92 three-terminal package and provides a current through an artificial midpoint up to 20 mA in any direction with a current consumption of not more than 0.25 mA and a dynamic output resistance of not more than 0.22 Ohm. In the event that the load may not be connected to a common point of the circuit or to any of the power buses, you can use the simplest option for forming an artificial zero point on a resistive divider (Fig. 9, a), but with a bridge amplifying circuit (Fig. 9, e).
In this circuit, the inverting follower on OU2 creates a potential at the lower pole of the load RL that is antiphase with respect to the potential of its upper pole. Here, a current equal to V IN / R1 flows into the artificial zero point, so the resistance of the resistor R1 should be taken as large as possible, otherwise it is possible not zero point symmetry. Additional advantages of this circuit: increase in the maximum voltage amplitude
at the load twice at the same supply voltage and a noticeable increase in efficiency at the full range of the output voltage.
Dynamic range expansion
Reducing the supply voltage of the op-amp from conventional +15 V to unipolar 5 V significantly reduces the amplitude range of the input and output voltages. The amplitude range in this case can be defined as the difference between the maximum and minimum possible input (output) voltages. The use of amplifiers designed for bipolar supply is also possible with unipolar supply, but, firstly, with a low potential difference between the supply terminals, not all types of such op-amps have acceptable characteristics (for example, gain), and secondly, the amplitude range their output voltages are relatively small due to the rather high saturation voltages of the output stage transistors. The output voltage swing of conventional general purpose amplifiers does not reach the upper and lower potentials of the power supply by 1 ... 2 V at rated load. When such an amplifier is powered from a unipolar 5 V source, the amplitude range of the output will be 1 ... 3 V. This means a serious decrease in the signal-to-noise ratio and a decrease in the resolution of the circuit.
Currently, for operation from low-voltage power supplies, including unipolar ones, a large number of op-amp models with a full output swing (“Rail-to-Rail”) have been developed. The output voltage of such amplifiers during idle operation can vary practically from the potential of the negative pole of the power supply to the potential of the positive pole.
The circuitry of the output stages of full swing amplifiers and conventional op amps is different. The output stage of conventional op amps is built according to a common collector circuit on complementary transistors (Fig. 10, a).
When using such a circuit solution, the minimum voltage drop across the output transistor cannot be reduced in principle. As follows from the diagram in Fig. 10, a, the current source I must provide the collector current of the transistor of the voltage amplification stage VT3 and the base current of the output transistor VT1. For normal operation of the current source circuit, a voltage drop across it VT1 of at least 1 V is necessary. The rest of the total voltage drop falls on the output transistor. You can reduce the minimum drop on the transistors of the output stage by turning on the transistors in the output stage according to the common emitter circuit (Fig. 10, b). According to this scheme, an output stage is built, for example, the AD823 op-amp from Analog Devices.
On fig. Figure 11 shows the saturation voltage V SAT of the output transistors of this amplifier as a function of the load current I L for the maximum (V S -V OH) and minimum (V OL) output voltages. Obviously, when the amplifier is idling, the maximum output voltage almost reaches the supply voltage, and the minimum one differs little from zero. Even better idle performance is provided by amplifiers in which the output stage is built on complementary MOSFETs (Fig. 10, c).
The fully open resistances of the upper and lower MOSFETs of the output stage of the op amp type TLC2272 from Texas InstRuments are 500 and 200 ohms, respectively, when the amplifier is powered from a unipolar 5 V source.
If the load R L is connected between the output of the op-amp and the common point of the circuit, as shown in fig. 4, then at low output voltages, the output current is also small, and the voltage on the open lower transistor of the amplifier is very close to zero (fractions of a millivolt). If the load current is high, and the load is connected by another terminal to the plus of the power supply or an artificial zero point, the voltage at the fully open output transistor can reach large values (more than 1 V). Some applications require not only the full swing of the op-amp output, but also the full swing (Rail-to-Rail) input common mode voltage V SP (full swing input). This is necessary, for example, in a non-inverting repeater circuit that matches a signal sensor with an analog-to-digital converter. For some applications, it is necessary that the range of input signals be below the potential of the common bus by 0.2 ... 0.3 V. This is required for unipolar power supply of the inverting amplifier, where a negative voltage must be applied to the input (Fig. 3), for example, in the photometer circuit (Fig. 4), where the polarity of the voltage at the inverting input of the op-amp is somewhat lower than at the non-inverting one. Amplifiers with full swing input are noticeably more complex in circuitry than conventional ones. They have no other advantages, except for the ability to work with a wide range of the input common-mode signal. Therefore, they should only be used where the full swing of the entry is really required.
On fig. 12, and a diagram of the differential input stage of a conventional op-amp is shown. It consists of two coordinated structures. In order for the input signal to reach the potential of the common bus, p-n-p transistors are used.
This construction allows you to apply the potential of a common bus to the input without disrupting the operation of the input stage. At
at lower common-mode input voltage, the front-end behavior becomes unpredictable. Often there is an inversion of the inputs, in which the sign of the feedback changes, and the op-amp goes into the trigger mode
(the so-called "snap"). Since the voltage at the current source V IT in the circuit in fig. 12 and should not be
less than 0.4 V (otherwise it simply will not work), and the base-emitter voltage of the transistors V BE in active mode
is approximately 0.6V, then the input common-mode signal must be at least 1V below the supply voltage.
On fig. 12, b shows a differential cascade on n-channel field-effect transistors with a control p-n junction (JFET transistors). Since the threshold source-gate voltage of such transistors is -2 ... -3 V, it is easy to ensure the normal operation of the input stage of the op-amp with small negative common-mode input voltages. This is how the input stage of the AD823 op amp is built with full output swing. This amplifier operates normally at -1 V< V СФ < V S –1 В.
If the operation of the op-amp with the full range of the input voltage is required, then a double complementary differential stage is used (Fig. 12, c). The bipolar variant shown in Fig. 12, c, is used in op-amps of the TLV245x and OP196 types, the CMOS version of this circuit is in the TLV247x and AD853x. From the diagram it is clear that both differential amplifiers of the input stage are controlled simultaneously. A differential amplifier (DU) with p-n-p transistors operates up to a maximum level of input signals 1 V below the supply voltage. For normal operation of the n-p-n-amplifier, a common-mode signal of at least 1 V is required. Thus, in the 1 V zone
the boundaries of these zones, which can cause distortion of the amplified signal. You can reduce these distortions by connecting in series with the non-inverting input resistor RC (Fig. 3), the resistance of which is determined by the formula
Rc = R1R2/R1+R2 (5)
In table. 2 shows the main parameters (typical values) of some types of op amps designed to operate with a single supply.
Op-amp circuits with unipolar power supply
Linear Voltage Regulator
A diagram of a linear voltage stabilizer on an op-amp with a regulating transistor connected according to the circuit with OK is shown in fig. 13, a.
The circuit contains an op-amp connected according to the circuit of a non-inverting amplifier with negative voltage feedback, a reference voltage source V REF and a regulating n-p-n-transistor VT connected in series with the load. The output voltage V OUT is controlled by a negative feedback circuit made on a resistive divider R 1 R 2 . The op amp plays the role of an error amplifier. The error here is the difference between the reference voltage V REF given by the reference voltage source (ION) and
divider output voltage R 1 R 2
ΔV = V REF - V OUT R1/R1+R2. (6)
The operational amplifier is powered by a unipolar positive voltage. At the same time, operational amplifiers designed for +15 V bipolar supply can be used in stabilizer circuits.
with an input voltage of up to 30 V. The stabilized output voltage is limited from below by the minimum common-mode input voltage of the op-amp, and from above by the sum of the saturation voltage of the op-amp and the saturation voltage of the base-emitter of the regulating transistor, i.e., the minimum allowable input-output voltage of the stabilizer when used
conventional op amps will be large (about 3 V). On fig. 13, b shows a diagram of a stabilizer with a reduced input / output voltage (the so-called LDO stabilizer). Here the regulating transistor is on
according to the scheme with OE, so there may be problems with stability. Minimum allowable input/output voltage
this circuit is limited only by the saturation voltage of the collector-emitter of the regulating transistor VT.
precision rectifier
Remarkable in simplicity, the circuit of a full-wave precision rectifier is shown in fig. fourteen .
It does not contain diodes at all. However, only op-amps with a full range of input and output voltages (Rail-to-Rail) can be used in this circuit. Amplifiers are necessarily powered from a unipolar source. If V IN >0, then the op-amp operates as a non-inverting follower. In this case, the OU2 amplifier operates in differential mode and V OUT \u003d V IN. At V IN<0 усилитель ОУ1 уходит в отрицательное насыщение, напряжение на его выходе становится равным нулю (питание однополярное!). Тогда усилитель ОУ2 переходит в режим инвертирующего повторителя, поэтому V OUT = –V IN . Как следствие, V OUT = |V IN |.
Amplifier op-amp 2 always operates in linear mode, and the potential of the non-inverting input op-amp at V IN<0 становится ниже потенциала отрицательного полюса источника питания. Не все операционные усилители это допускают. Например, сдвоенный ОУ ОР291 как нельзя лучше подходит для этой схемы. Его входы защищены от дифференциального перенапряжения встречно-параллельно включенными диодами, причем в цепи баз входных транзисторов включены резисторы сопротивлением в 5 кОм. Это позволяет усилителю выдерживать при однополярном питании входное синфазное напряжение до –15 В. В этом случае резистор R1 можно не включать. Иное дело - сдвоенный усилитель ОР296. Он не имеет защитных резисторов, и при его применении в этой схеме необходимо включать резистор R1=2 кОм.
The manufacturer recommends an input signal range of ±1 V for this circuit with a 5-volt supply. Due to the fact that the op-amp 1 takes a long time to get out of saturation, the frequency range of the circuit turns out to be rather narrow - for the op-amp OP291 it is 0 ... 2 kHz.
Current measurement circuit
To measure high currents in a line under a relatively high potential, the circuit shown in fig. 15 .
The current flowing through the load creates a voltage V IN across the shunt Rsh, which here is the current sensor. We assume the OU is ideal. Then no current flows through the inverting input of the amplifier, and since the voltage between the differential inputs of the amplifier is zero, the voltage V IN is applied to the left resistor R. The current through the resistor R and the collector of the transistor VT
l c \u003d V IN /R \u003d l L R w /R (7)
Neglecting the base current of the transistor, we find the output voltage of the circuit
V OUT \u003d l C R T \u003d l L R T R w / R (8)
It is this scheme that the Burr-Brown INA168 current meter is made of (the crystal boundaries are shown in Fig. 15 by a dashed line). It allows up to 60V common-mode input voltage and a shunt voltage gain of up to 100. The current drawn by the IC is only 50uA. The LT1787 microcircuit of a similar purpose is built symmetrically, since it incorporates an amplifier with differential inputs and outputs and a load in the form of a current mirror. Allowable common mode voltage is also 60 V. Dynamic range -12 bits (72 dB). The MAX471 current meter chip has a shunt resistor on the chip, designed for a current of up to 3 A, while the MAX4372 does not have such a resistor, but its conversion error does not exceed 0.18%.
D/A Converter
with voltage output
A combination of a current output DAC, such as the 12-bit AD7541A, and a full swing op amp is shown in Figure 1. 16 .
Here, the inverse inclusion of the resistive matrix R-2R is used. The op-amp is connected according to the scheme of a non-inverting amplifier with a gain of 2. TL431 can be used as a reference voltage source. The output voltage of the circuit is given by
VOUT = 2V REF /4096*DI, (9)
where DI is the input code.
conclusions
Bipolar powered op amps can operate in single source circuits, but their input and output range may be too narrow. Op-amps designed to operate with a single source, in turn, can also operate in circuits with a bipolar supply. It is only necessary that the potential difference between the positive and negative source does not exceed the maximum allowable supply voltage for this type of amplifier. If it is required to amplify AC signals, then with a unipolar supply it is advisable to use bias circuits and coupling capacitors (Fig. 7) .
If the DC input signal is bipolar, then bias circuits can be used, but it is more convenient
introduction to the circuit of an artificial zero point. If it is intended to operate with input signals below the common bus potential with a single supply, measures should be taken, if necessary, to protect the amplifier inputs.
Georgy Volovich,
[email protected]
Literature
1. Mancini R. Single Supply Op Amp Design Techniques // Application RepoRt SLOA030. - Texas Instruments
IncoRporated. - OctobeR 1999. - 23 p.
2. Volovich G. Stability of linear integral voltage stabilizers. - Circuitry, 2001. No. 11.
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