Analog computer with operational amplifiers
An analog computer is an analog computer (AVM); it is a continuous computer that processes analog data (continuous information).
TSB gives this definition of an analog computer.
An analog computer (AVM), a computer in which each instantaneous value of a variable participating in the initial ratios is associated with the instantaneous value of another (machine) quantity, which often differs from the original physical nature and by a scale factor. Each elementary mathematical operation on machine quantities, as a rule, corresponds to a certain physical law that establishes mathematical relationships between physical quantities at the output and input of the decisive element (for example, Ohm and Kirchhoff laws for electric circuits, expression for the Hall effect, Lorentz force, etc. .).
It is worth noting that an analog computer is not only electric, but also mechanical, hydraulic and even pneumatic.
Despite the apparent anachronism, analog computing is widely used in modern life. Automotive automatic transmission is an example of a hydromechanical analogue computer, in which when the torque changes, the fluid in the hydraulic actuator changes pressure, which allows you to get a change in the gear ratio.
Analog processing of electrical signals occupies an important place in industrial electronics. Most types of primary converters of physical quantities are sources of analog signals, and many actuators in the control objects are controlled by a continuously changing electric current. Even control systems based on digital computing systems cannot refuse analog signal processing and are interfaced with control objects and sensors using analog and analog-to-digital devices.
In connection with the volume of material that I would like to present, I plan to write a series of articles. I propose to the reader’s court the first part, which will briefly tell the story of the creation of an operational amplifier in the form as we know it.
The history of the use of AVM has several millennia. Those interested can start their searches with a wikipedia article .
But in this article I will focus only on dates that directly swing the history of the creation of an electronic operational amplifier. And I will start with a date that, at first glance, has nothing to do with the topic of the article.
1614 Scottish mathematician John Napier publishes the “Logarithm Canon”, which began as follows: “Realizing that there is nothing more boring and tedious in mathematics than multiplying, dividing, extracting square and cubic roots, and that these operations are a waste of time and an inexhaustible source of elusive mistakes, I decided to find a simple and reliable means to get rid of them ”.
Let me remind you of some properties of logarithms. From the properties of the logarithm, it follows that instead of the time-consuming multiplication of multivalued numbers, it is enough to find (from the tables) and add their logarithms, and then perform potentiation from the same tables, that is, find the value of the result by its logarithm. Doing the division differs only in that the logarithms are subtracted.
In the form of formulas, it looks like this:
lg (xy) = lg (x) + lg (y) for multiplication
lg (x / y) = lg (x) - lg (y) for division
Neper created the first tables of logarithms of trigonometric functions.
Students of the pre-computer era should remember what four-digit Bradis tables are.
1622 English amateur mathematician William Otredperhaps created one of the most successful analog computing mechanism - the slide rule.
Fans of handicrafts can assemble their pocket analog calculator according to these instructions and learn how to use it until December 2012. Suddenly it will come in handy ...
But still, I will skip the history of the development of non-electronic analog computers and go directly to the topic of our article.
1904 In November 1904, John Ambrose Fleming invented a rectifier on a two-electrode electron lamp, which he called an oscillating valve. The invention is also called: a lamp with a thermal cathode, a vacuum diode, a kenotron, a thermionic lamp, a Fleming valve.
1906 AmericanLee de Forest added a “grid” control to the electronic lamp and created a radio frequency detector called audion, but Fleming accused him of copying his ideas. The device of de Forest was soon modified by him and Edwin Armstrong and used in the first electronic amplifier, and the lamp itself was called a triode .
1927 - Herold Steven Black at Bell Telephone Laboratories Research Center creates a negative feedback amplifier. Fig. 1. Amplifier with negative feedback.
At its core, all electronic devices (electron tube, bipolar transistor, MOS transistor) operate non-linearly. Negative feedback corrects this shortcoming by sacrificing gain to improve linearity (reduce distortion). But negative feedback can, under certain conditions, become positive, and then the amplifier will turn into a generator. Subsequently, Harry Nyquist developed a theory on how to make the OS stable.
30-40 years In the 30s, George A. Philbrick), while working at Foxboro Corporation, developed analogue process control simulation circuits with vacuum tubes and passive elements. Philbrick developed many interesting circuits, and some were the ancestors of the operational amplifier.
Although amplifiers using both closed-loop and non-feedback amplifiers were improved in the late 1930s and throughout the 1940s, several very interesting developments in the field of differential amplifiers are worth noting.
In the 30s there was a need for low-level signals received from living tissue. For this, various tube amplifiers were used, such amplifiers were often called the "biological amplifier".
In 1934, W. HC Matthews, a biologist by profession, described a differential amplifier circuit. The amplifier did have differential inputs, but since the common cathodes were tied directly to a common power source, it was not optimized to minimize the common-mode voltage difference at the inputs. Note that in those days, common-mode signals are often referred to as push-push signals to indicate phase signals at both inputs.
In 1936, Alan Blumleindeveloped the ideas of Matthews, by shifting the common cathodes of a differential pair through common resistance to earth. Alan Blumlein received a patent for his amplifier, but the patent dealt with broadband signals, not biological ones. However, this was a definite step forward compared to the Matthews amplifier, as it provides better common-mode error detection. Amplifier circuits Matthews and Blumlein shown in Fig. 2. Fig. 2. The scheme of the differential amplifier. 1941 During the work on gun data computer under the M9 index, Bell Labs received a patent No. 2,401,779 for Summing amplifier . Schematic diagram and component values for "Summing Amplifier" ( US Patent 2,401,779, assigned to Bell Telephone Laboratories, Inc.)
Fig. 3. Scheme and list of components of the summing amplifier.
This design uses three vacuum tubes to achieve a gain of 90 dB and is controlled by a voltage of ± 350 V. The circuit has a single inverting input, and not a differential inverting and non-inverting inputs, as are common in today's operational amplifiers. The use of this scheme in a military computer M9 together with the radar system SCR584 yielded 90% accuracy of anti-aircraft fire. For the first time this system was applied in 1944 during the landing of the allied forces in Italy .
1947 At Columbia University of New York, in the course of research work to improve analog computing for military purposes, the term operational amplifier(OU). The design of the op-amp was developed by Loebe Julie. This scheme had two major innovations. Means were used to reduce the zero drift of the amplifier and, more importantly, it was the first design of an operational amplifier that will have two inputs (one invert, the other non-invert).
1953 In 1946, after leaving the army, George A. Philbrick created a company named himself George A. Philbrick Researches, Inc., (GAP / R) and began creating operational amplifiers. His work played an important role in the development of OS.
Soon, in January 1953 , the first commercial K2-W. At the same time, its cost was about $ 20. The K2-W used two 12AX7 dual triodes and was packaged in a standard eight-pin connector. The op-amp was built by Loeb Julie. Working at a voltage of ± 300 V, the op-amp could work with voltages at the output and input of up to ± 50 V and had a gain of more than 15,000.
If the reader has to create circuits on this op-amp, then he can study the datasheet on links 1 , page 2 . For the rest, I just give Figure 4. Figure 4. K2-W. Photography and electrical concept. 50 years Tube amplifiers improved. The circuitry solutions improved, the gain, accuracy increased, and energy consumption decreased. But by the beginning of the 60s, the sunset of the warm era had begun
tube operational amplifier and the transistor entered the scene and subsequently, integrated circuits.
1947 William Shockley , John Bardin, and Walter Brattain at Bell Labs for the first time created an operational bipolar transistor , demonstrated on December 16th. On December 23, the official presentation of the invention took place and this date is considered the day of the invention of the transistor. According to manufacturing technology, he belonged to the class of point transistors.
In May 1954. Gordon Teal of Texas Instruments has developed a silicon transistor.
In 1958, Jack Kilbyfrom Texas Instruments invented the integrated circuit, now known as universal ICs. Kilby's work, however, was not the only one. In early 1959, Robert Noyce , an engineer at Fairchild Semiconductor , also developed the concept of IP. After 10 years, in 1968, Robert Neuss and Gordon Moore will leave Fairchild Semiconductor and organize Intel , but that's another story.
The core of the Noyce concept was actually closer to the concept of today's ICs, since it uses the interconnections of metal layers between transistors and resistors. Kilby IPs, on the other hand, used wire connections.
One version of the history of the creation of IP is presented in an article inVirtual computer museum . Fig. 5. The layout of the first IS Kilby. Fig. 6. Illustration for the patent of Noyce. 1961 Be that as it may, as a result, in 1961 the first integrated circuits of operational amplifiers were produced. It was a GAP / R P45 worth about $ 120. These operational amplifiers were actually small boards with edge connectors. As a rule, they were equipped with carefully selected resistors in order to improve the characteristics of the opamp, such as bias voltage and drift. The GAP / R P45 op amp had a gain of 94 dB and was powered by ± 15 V. The op amp had to deal with signals in the ± 10V range. Subsequently, these voltages became a kind of standard.
Fig. 7. Shelter GAP / R P45. Photography and electrical concept.
1961 George A. Philbrick creates a varactor bridge operational amplifier circuit.
In this circuit, the voltage of variable capacitors (varactors) are used in the input stage of the operational amplifier. As a result of using the varactor bridge, the lowest input current of any op-amp was achieved. Even less than the lamps.
Fig. 8 illustrates a block diagram of a varactor bridge op-amp. There are four main components, the front part consists of a bridge circuit and a circuit for a high-frequency generator, an AC amplifier for amplifying the error voltage of the bridge, a synchronous phase detector for converting AC error for the corresponding DC error, and finally, an output amplifier that provides additional DC amplification and device loads. Fig. 8. Block diagram of a varactor bridge operational amplifier. The circuit works as follows: a small error in the DC voltage Vin
applies to the selected varactor diodes D1 and D2 and causes an imbalance of the AC bridge, which is fed into the AC amplifier. This AC voltage will be phase shifted depending on the DC error voltage. The remaining parts of the circuit amplify and detect a DC error. Philbrick released the GAP / R P2 operational amplifier. Released in 1966, the modified GAP / R SP2A op amp could amplify the input current of the order of ± 10pA (10 −12 ).
In 1965, Ray State Matthew Lorber created Analog Devices, Inc. (ADI). Soon, Lewis R. Smith created the varactor amplifier model 301, as well as his successors, models 310 and 311. These projects were able to significantly increase the accuracy of input currents to ± 10fA (10 −15 ) (about 3 orders of magnitude) below GAP / R P2). Interestingly, 310 and 311 models were sold at prices of about $ 75. These amplifiers are still available in limited quantities in
1967. It is also worth noting that ADI has done a lot to popularize the use of op amps. So, in 1967 she began to issue the Analog Dialogue Magazinethat comes out to this day. The online version of the magazine is a forum for the exchange of solutions in the field of circuitry and software for real devices and signal processing systems. It discusses technologies and methods for analog, digital and mixed signals. Operating as a gateway to ADI technology, the Analog Dialogue is published monthly on the Internet. Selected technical articles are also presented in quarterly print media .
1962 Alan Perlman and Roger Noble leave GAP / R and form a small company, Nexus Research Laboratory, Inc.They were the first to produce op-amps packaged in rectangular modules with pins adapted for mounting on printed circuit boards. This design turned the op-amp into a “black box”, which was easy to consider as a separate element of the circuit. The modules became so popular that GAP / R was forced to release its amplifier in a similar package. Fig. 9. Shelter GAP / R PP65. Photography and electrical concept. 1963 The μA702 of Fairchild Semiconductor Corporation became the first monolithic op-amp integrated circuit. μA702 was developed by a young engineer Robert J. (Bob) Widlar
. Vidlar's professional activities during the whole seven years (1963-1970) largely determined the development of analog microelectronics. But his μA702 certainly did not take the world by storm. It was not well received, due to unusual properties - excess supply voltage, low gain, etc. Nevertheless, despite these shortcomings, some important design trends for the IC were identified by the μA702.
1965 μA709 Released. He significantly improved the characteristics of μA702. This includes a larger gain (45,000 or ~ 94dB), I / O voltage expanded to ± 10V, reduction of the input current to 200nA and increase of the output current. The amplifier was powered by a voltage of ± 15V. Frequency compensation was achieved by two RC circuits between pins 1-8, and 6-5. The μA709 quickly became the standard and was produced for several decades. Fig. 10 shows a schematic diagram of a μA709. Fig. 10. Electrical circuit diagram μA709. Despite a fairly strong improvement over the circuit compared to the μA702, the amplifier still had problems. 1967 Not wanting to rest on the laurels of his op-amp μA702 and μA709, Bob Widlar switched to another company, National Semiconductor Corporation (NSC). His next integrated circuit design,
LM101 , was launched in 1967. The LM101 used a simple two-stage topology, which was the solution to the problems of μA709. In addition, it was a design of operational amplifiers, which was subsequently followed by many manufacturers. A simplified diagram of the LM101 is shown in Figure 11. Fig. 11. The simplified circuit LM101. The objectives of the LM101 project were to eliminate μA709 problems such as: • There is no short circuit protection. • Comprehensive compensation frequencies. • Sensitivity to overvoltage differential input. • Excessive power dissipation and limited power range. • Sensitivity to capacitive loads.
The new LM101 design resolved μA709 problems, and added a few more improvements. The gain increased to 160,000 (~ 104 dB), the useful power range increased from ± 5V to ± 20V. For easy upgrades, the LM101 used the same pins as the μA709 for input, output, and power.
1968 Less than a year after the release of the LM101, Fairchild in 1968 released the μA741 op amp , designed by Dave Fallager. The simplified circuit μA741 is shown in Figure 12. Fig. 12. Simplified circuit μA741.
Although there are obvious differences in the circuits, in μA741 the signal path is equivalent to LM101, and it provides similar behavior in terms of input short circuit and overvoltage protection, and has a comparable bandwidth. A distinctive feature of the μA741 was the presence of a 30pF compensation capacitor in the chip, it soon became the standard.
The LM101, with a user-added capacitor, were functionally equivalent to μA741. However, ease of use proved to be more valuable to users than flexibility. National Semiconductor subsequently made a hybrid package of an LM101 chip and a 30pF capacitor, but it was μA741 that became the standard.
On Wikipedia, an entire article is devoted to this amplifier .
1970 yearJohn Cadigan, working at ADI, creates a high-speed operational amplifier. The distinctive ability of this op-amp was the use of field-effect transistors in the input stage. The op-amp was implemented as a hybrid integrated circuit. Below I will give a diagram and a photo of the more advanced op amp HQS-050 , released in 1977. Fig. 13. HSQ-050. Schematic diagram and photo. I think it’s worth stopping here. And as a conclusion, I will give a diagram of another op-amp, which will allow us to assess the level of circuitry of modern operational amplifiers. Figure 14. AD549. The circuit is electrical in principle. In the second part, I will briefly review the internal circuitry of an operational amplifier.
The use of operational amplifiers as elements of analog computing devices I will present in the third part.
The main source for this article was the book .
http://ru.wikipedia.org/wiki/
http://www.computer-museum.ru/
http://www.computerhistory.org/
TSB gives this definition of an analog computer.
An analog computer (AVM), a computer in which each instantaneous value of a variable participating in the initial ratios is associated with the instantaneous value of another (machine) quantity, which often differs from the original physical nature and by a scale factor. Each elementary mathematical operation on machine quantities, as a rule, corresponds to a certain physical law that establishes mathematical relationships between physical quantities at the output and input of the decisive element (for example, Ohm and Kirchhoff laws for electric circuits, expression for the Hall effect, Lorentz force, etc. .).
It is worth noting that an analog computer is not only electric, but also mechanical, hydraulic and even pneumatic.
Despite the apparent anachronism, analog computing is widely used in modern life. Automotive automatic transmission is an example of a hydromechanical analogue computer, in which when the torque changes, the fluid in the hydraulic actuator changes pressure, which allows you to get a change in the gear ratio.
Analog processing of electrical signals occupies an important place in industrial electronics. Most types of primary converters of physical quantities are sources of analog signals, and many actuators in the control objects are controlled by a continuously changing electric current. Even control systems based on digital computing systems cannot refuse analog signal processing and are interfaced with control objects and sensors using analog and analog-to-digital devices.
In connection with the volume of material that I would like to present, I plan to write a series of articles. I propose to the reader’s court the first part, which will briefly tell the story of the creation of an operational amplifier in the form as we know it.
Part one. A brief history of the creation of an operational amplifier.
The history of the use of AVM has several millennia. Those interested can start their searches with a wikipedia article .
But in this article I will focus only on dates that directly swing the history of the creation of an electronic operational amplifier. And I will start with a date that, at first glance, has nothing to do with the topic of the article.
1614 Scottish mathematician John Napier publishes the “Logarithm Canon”, which began as follows: “Realizing that there is nothing more boring and tedious in mathematics than multiplying, dividing, extracting square and cubic roots, and that these operations are a waste of time and an inexhaustible source of elusive mistakes, I decided to find a simple and reliable means to get rid of them ”.
Let me remind you of some properties of logarithms. From the properties of the logarithm, it follows that instead of the time-consuming multiplication of multivalued numbers, it is enough to find (from the tables) and add their logarithms, and then perform potentiation from the same tables, that is, find the value of the result by its logarithm. Doing the division differs only in that the logarithms are subtracted.
In the form of formulas, it looks like this:
lg (xy) = lg (x) + lg (y) for multiplication
lg (x / y) = lg (x) - lg (y) for division
Neper created the first tables of logarithms of trigonometric functions.
Students of the pre-computer era should remember what four-digit Bradis tables are.
1622 English amateur mathematician William Otredperhaps created one of the most successful analog computing mechanism - the slide rule.
Fans of handicrafts can assemble their pocket analog calculator according to these instructions and learn how to use it until December 2012. Suddenly it will come in handy ...
But still, I will skip the history of the development of non-electronic analog computers and go directly to the topic of our article.
1904 In November 1904, John Ambrose Fleming invented a rectifier on a two-electrode electron lamp, which he called an oscillating valve. The invention is also called: a lamp with a thermal cathode, a vacuum diode, a kenotron, a thermionic lamp, a Fleming valve.
1906 AmericanLee de Forest added a “grid” control to the electronic lamp and created a radio frequency detector called audion, but Fleming accused him of copying his ideas. The device of de Forest was soon modified by him and Edwin Armstrong and used in the first electronic amplifier, and the lamp itself was called a triode .
1927 - Herold Steven Black at Bell Telephone Laboratories Research Center creates a negative feedback amplifier. Fig. 1. Amplifier with negative feedback.
At its core, all electronic devices (electron tube, bipolar transistor, MOS transistor) operate non-linearly. Negative feedback corrects this shortcoming by sacrificing gain to improve linearity (reduce distortion). But negative feedback can, under certain conditions, become positive, and then the amplifier will turn into a generator. Subsequently, Harry Nyquist developed a theory on how to make the OS stable.
30-40 years In the 30s, George A. Philbrick), while working at Foxboro Corporation, developed analogue process control simulation circuits with vacuum tubes and passive elements. Philbrick developed many interesting circuits, and some were the ancestors of the operational amplifier.
Although amplifiers using both closed-loop and non-feedback amplifiers were improved in the late 1930s and throughout the 1940s, several very interesting developments in the field of differential amplifiers are worth noting.
In the 30s there was a need for low-level signals received from living tissue. For this, various tube amplifiers were used, such amplifiers were often called the "biological amplifier".
In 1934, W. HC Matthews, a biologist by profession, described a differential amplifier circuit. The amplifier did have differential inputs, but since the common cathodes were tied directly to a common power source, it was not optimized to minimize the common-mode voltage difference at the inputs. Note that in those days, common-mode signals are often referred to as push-push signals to indicate phase signals at both inputs.
In 1936, Alan Blumleindeveloped the ideas of Matthews, by shifting the common cathodes of a differential pair through common resistance to earth. Alan Blumlein received a patent for his amplifier, but the patent dealt with broadband signals, not biological ones. However, this was a definite step forward compared to the Matthews amplifier, as it provides better common-mode error detection. Amplifier circuits Matthews and Blumlein shown in Fig. 2. Fig. 2. The scheme of the differential amplifier. 1941 During the work on gun data computer under the M9 index, Bell Labs received a patent No. 2,401,779 for Summing amplifier . Schematic diagram and component values for "Summing Amplifier" ( US Patent 2,401,779, assigned to Bell Telephone Laboratories, Inc.)
Fig. 3. Scheme and list of components of the summing amplifier.
This design uses three vacuum tubes to achieve a gain of 90 dB and is controlled by a voltage of ± 350 V. The circuit has a single inverting input, and not a differential inverting and non-inverting inputs, as are common in today's operational amplifiers. The use of this scheme in a military computer M9 together with the radar system SCR584 yielded 90% accuracy of anti-aircraft fire. For the first time this system was applied in 1944 during the landing of the allied forces in Italy .
1947 At Columbia University of New York, in the course of research work to improve analog computing for military purposes, the term operational amplifier(OU). The design of the op-amp was developed by Loebe Julie. This scheme had two major innovations. Means were used to reduce the zero drift of the amplifier and, more importantly, it was the first design of an operational amplifier that will have two inputs (one invert, the other non-invert).
1953 In 1946, after leaving the army, George A. Philbrick created a company named himself George A. Philbrick Researches, Inc., (GAP / R) and began creating operational amplifiers. His work played an important role in the development of OS.
Soon, in January 1953 , the first commercial K2-W. At the same time, its cost was about $ 20. The K2-W used two 12AX7 dual triodes and was packaged in a standard eight-pin connector. The op-amp was built by Loeb Julie. Working at a voltage of ± 300 V, the op-amp could work with voltages at the output and input of up to ± 50 V and had a gain of more than 15,000.
If the reader has to create circuits on this op-amp, then he can study the datasheet on links 1 , page 2 . For the rest, I just give Figure 4. Figure 4. K2-W. Photography and electrical concept. 50 years Tube amplifiers improved. The circuitry solutions improved, the gain, accuracy increased, and energy consumption decreased. But by the beginning of the 60s, the sunset of the warm era had begun
tube operational amplifier and the transistor entered the scene and subsequently, integrated circuits.
1947 William Shockley , John Bardin, and Walter Brattain at Bell Labs for the first time created an operational bipolar transistor , demonstrated on December 16th. On December 23, the official presentation of the invention took place and this date is considered the day of the invention of the transistor. According to manufacturing technology, he belonged to the class of point transistors.
In May 1954. Gordon Teal of Texas Instruments has developed a silicon transistor.
In 1958, Jack Kilbyfrom Texas Instruments invented the integrated circuit, now known as universal ICs. Kilby's work, however, was not the only one. In early 1959, Robert Noyce , an engineer at Fairchild Semiconductor , also developed the concept of IP. After 10 years, in 1968, Robert Neuss and Gordon Moore will leave Fairchild Semiconductor and organize Intel , but that's another story.
The core of the Noyce concept was actually closer to the concept of today's ICs, since it uses the interconnections of metal layers between transistors and resistors. Kilby IPs, on the other hand, used wire connections.
One version of the history of the creation of IP is presented in an article inVirtual computer museum . Fig. 5. The layout of the first IS Kilby. Fig. 6. Illustration for the patent of Noyce. 1961 Be that as it may, as a result, in 1961 the first integrated circuits of operational amplifiers were produced. It was a GAP / R P45 worth about $ 120. These operational amplifiers were actually small boards with edge connectors. As a rule, they were equipped with carefully selected resistors in order to improve the characteristics of the opamp, such as bias voltage and drift. The GAP / R P45 op amp had a gain of 94 dB and was powered by ± 15 V. The op amp had to deal with signals in the ± 10V range. Subsequently, these voltages became a kind of standard.
Fig. 7. Shelter GAP / R P45. Photography and electrical concept.
1961 George A. Philbrick creates a varactor bridge operational amplifier circuit.
In this circuit, the voltage of variable capacitors (varactors) are used in the input stage of the operational amplifier. As a result of using the varactor bridge, the lowest input current of any op-amp was achieved. Even less than the lamps.
Fig. 8 illustrates a block diagram of a varactor bridge op-amp. There are four main components, the front part consists of a bridge circuit and a circuit for a high-frequency generator, an AC amplifier for amplifying the error voltage of the bridge, a synchronous phase detector for converting AC error for the corresponding DC error, and finally, an output amplifier that provides additional DC amplification and device loads. Fig. 8. Block diagram of a varactor bridge operational amplifier. The circuit works as follows: a small error in the DC voltage Vin
applies to the selected varactor diodes D1 and D2 and causes an imbalance of the AC bridge, which is fed into the AC amplifier. This AC voltage will be phase shifted depending on the DC error voltage. The remaining parts of the circuit amplify and detect a DC error. Philbrick released the GAP / R P2 operational amplifier. Released in 1966, the modified GAP / R SP2A op amp could amplify the input current of the order of ± 10pA (10 −12 ).
In 1965, Ray State Matthew Lorber created Analog Devices, Inc. (ADI). Soon, Lewis R. Smith created the varactor amplifier model 301, as well as his successors, models 310 and 311. These projects were able to significantly increase the accuracy of input currents to ± 10fA (10 −15 ) (about 3 orders of magnitude) below GAP / R P2). Interestingly, 310 and 311 models were sold at prices of about $ 75. These amplifiers are still available in limited quantities in
1967. It is also worth noting that ADI has done a lot to popularize the use of op amps. So, in 1967 she began to issue the Analog Dialogue Magazinethat comes out to this day. The online version of the magazine is a forum for the exchange of solutions in the field of circuitry and software for real devices and signal processing systems. It discusses technologies and methods for analog, digital and mixed signals. Operating as a gateway to ADI technology, the Analog Dialogue is published monthly on the Internet. Selected technical articles are also presented in quarterly print media .
1962 Alan Perlman and Roger Noble leave GAP / R and form a small company, Nexus Research Laboratory, Inc.They were the first to produce op-amps packaged in rectangular modules with pins adapted for mounting on printed circuit boards. This design turned the op-amp into a “black box”, which was easy to consider as a separate element of the circuit. The modules became so popular that GAP / R was forced to release its amplifier in a similar package. Fig. 9. Shelter GAP / R PP65. Photography and electrical concept. 1963 The μA702 of Fairchild Semiconductor Corporation became the first monolithic op-amp integrated circuit. μA702 was developed by a young engineer Robert J. (Bob) Widlar
. Vidlar's professional activities during the whole seven years (1963-1970) largely determined the development of analog microelectronics. But his μA702 certainly did not take the world by storm. It was not well received, due to unusual properties - excess supply voltage, low gain, etc. Nevertheless, despite these shortcomings, some important design trends for the IC were identified by the μA702.
1965 μA709 Released. He significantly improved the characteristics of μA702. This includes a larger gain (45,000 or ~ 94dB), I / O voltage expanded to ± 10V, reduction of the input current to 200nA and increase of the output current. The amplifier was powered by a voltage of ± 15V. Frequency compensation was achieved by two RC circuits between pins 1-8, and 6-5. The μA709 quickly became the standard and was produced for several decades. Fig. 10 shows a schematic diagram of a μA709. Fig. 10. Electrical circuit diagram μA709. Despite a fairly strong improvement over the circuit compared to the μA702, the amplifier still had problems. 1967 Not wanting to rest on the laurels of his op-amp μA702 and μA709, Bob Widlar switched to another company, National Semiconductor Corporation (NSC). His next integrated circuit design,
LM101 , was launched in 1967. The LM101 used a simple two-stage topology, which was the solution to the problems of μA709. In addition, it was a design of operational amplifiers, which was subsequently followed by many manufacturers. A simplified diagram of the LM101 is shown in Figure 11. Fig. 11. The simplified circuit LM101. The objectives of the LM101 project were to eliminate μA709 problems such as: • There is no short circuit protection. • Comprehensive compensation frequencies. • Sensitivity to overvoltage differential input. • Excessive power dissipation and limited power range. • Sensitivity to capacitive loads.
The new LM101 design resolved μA709 problems, and added a few more improvements. The gain increased to 160,000 (~ 104 dB), the useful power range increased from ± 5V to ± 20V. For easy upgrades, the LM101 used the same pins as the μA709 for input, output, and power.
1968 Less than a year after the release of the LM101, Fairchild in 1968 released the μA741 op amp , designed by Dave Fallager. The simplified circuit μA741 is shown in Figure 12. Fig. 12. Simplified circuit μA741.
Although there are obvious differences in the circuits, in μA741 the signal path is equivalent to LM101, and it provides similar behavior in terms of input short circuit and overvoltage protection, and has a comparable bandwidth. A distinctive feature of the μA741 was the presence of a 30pF compensation capacitor in the chip, it soon became the standard.
The LM101, with a user-added capacitor, were functionally equivalent to μA741. However, ease of use proved to be more valuable to users than flexibility. National Semiconductor subsequently made a hybrid package of an LM101 chip and a 30pF capacitor, but it was μA741 that became the standard.
On Wikipedia, an entire article is devoted to this amplifier .
1970 yearJohn Cadigan, working at ADI, creates a high-speed operational amplifier. The distinctive ability of this op-amp was the use of field-effect transistors in the input stage. The op-amp was implemented as a hybrid integrated circuit. Below I will give a diagram and a photo of the more advanced op amp HQS-050 , released in 1977. Fig. 13. HSQ-050. Schematic diagram and photo. I think it’s worth stopping here. And as a conclusion, I will give a diagram of another op-amp, which will allow us to assess the level of circuitry of modern operational amplifiers. Figure 14. AD549. The circuit is electrical in principle. In the second part, I will briefly review the internal circuitry of an operational amplifier.
The use of operational amplifiers as elements of analog computing devices I will present in the third part.
List of sources used
The main source for this article was the book .
http://ru.wikipedia.org/wiki/
http://www.computer-museum.ru/
http://www.computerhistory.org/