A μA741 integrated circuit, one of the most successful operational amplifiers Type Invented First production 1967 Pin configuration. V+: non-inverting input. V−: inverting input. Vout: output. VS+: positive power supply.
VS−: negative power supply The power supply pins ( V S+ and V S−) can be labeled in different ways ( See ). Often these pins are left out of the diagram for clarity, and the power configuration is described or assumed from the circuit.
Op amp by ramakant gaikwad pdf free DOWNLOAD from mouse click enterprises is a free security tool that adds password protection to any folder in your system, even those on portable devices like usb flash drives. Op-Amps and Linear Integrated Circuits, 4th Edition. Ram Gayakwad. ©2000|Pearson| Available. Linear Integrated Circuits, 3rd Edition.
Circuit diagram symbol for an op-amp. Pins are labeled as listed above. An operational amplifier (often op-amp or opamp) is a high- electronic voltage with a and, usually, a output. In this configuration, an op-amp produces an output potential (relative to circuit ground) that is typically hundreds of thousands of times larger than the potential difference between its input terminals. Operational amplifiers had their origins in, where they were used to perform mathematical operations in many linear, non-linear, and frequency-dependent circuits.
The popularity of the op-amp as a building block in is due to its versatility. By using, the characteristics of an op-amp circuit, its gain, input and, etc. Are determined by external components and have little dependence on or in the op-amp itself. Op-amps are among the most widely used electronic devices today, being used in a vast array of consumer, industrial, and scientific devices. Many standard IC op-amps cost only a few cents in moderate production volume; however, some integrated or hybrid operational amplifiers with special performance specifications may cost over 100 in small quantities.
Op-amps may be packaged as components or used as elements of more complex integrated circuits. The op-amp is one type of. Other types of differential amplifier include the (similar to the op-amp, but with two outputs), the (usually built from three op-amps), the (similar to the instrumentation amplifier, but with tolerance to that would destroy an ordinary op-amp), and (usually built from one or more op-amps and a resistive feedback network). In a closed loop the output attempts to do whatever is necessary to make the voltage difference between the inputs zero. The inputs draw no current.: 177 The first rule only applies in the usual case where the op-amp is used in a closed-loop design (negative feedback, where there is a signal path of some sort feeding back from the output to the inverting input). These rules are commonly used as a good first approximation for analyzing or designing op-amp circuits.: 177 None of these ideals can be perfectly realized. A real op-amp may be modeled with non-infinite or non-zero parameters using equivalent resistors and capacitors in the op-amp model.
The designer can then include these effects into the overall performance of the final circuit. Some parameters may turn out to have negligible effect on the final design while others represent actual limitations of the final performance that must be evaluated. Real op-amps Real op-amps differ from the ideal model in various aspects.
DC imperfections Real operational amplifiers suffer from several non-ideal effects: Finite gain is infinite in the ideal operational amplifier but finite in real operational amplifiers. Typical devices exhibit open-loop DC gain ranging from 100,000 to over 1 million. So long as the (i.e., the product of open-loop and feedback gains) is very large, the circuit gain will be determined entirely by the amount of negative feedback (i.e., it will be independent of open-loop gain). In cases where must be very high, the feedback gain will be very low, and the low feedback gain causes low loop gain; in these cases, the operational amplifier will cease to behave ideally.
Finite The differential input impedance of the operational amplifier is defined as the impedance between its two inputs; the common-mode input impedance is the impedance from each input to ground.input operational amplifiers often have protection circuits that effectively short circuit any input differences greater than a small threshold, so the input impedance can appear to be very low in some tests. However, as long as these operational amplifiers are used in a typical high-gain negative feedback application, these protection circuits will be inactive. The input bias and leakage currents described below are a more important design parameter for typical operational amplifier applications. Non-zero Low output impedance is important for low-impedance loads; for these loads, the voltage drop across the output impedance effectively reduces the open loop gain.
In configurations with a voltage-sensing negative feedback, the output impedance of the amplifier is effectively lowered; thus, in linear applications, op-amp circuits usually exhibit a very low output impedance. Low-impedance outputs typically require high in the output stage and will dissipate more power, so low-power designs may purposely sacrifice low output impedance. Input current Due to requirements or, a small amount of current (typically 10 nanoamperes for op-amps, tens of picoamperes (pA) for input stages, and only a few pA for input stages) flows into the inputs. When large resistors or sources with high output impedances are used in the circuit, these small currents can produce large unmodeled voltage drops. If the input currents are matched, and the impedance looking out of both inputs are matched, then the voltages produced at each input will be equal.
Because the operational amplifier operates on the difference between its inputs, these matched voltages will have no effect. It is more common for the input currents to be slightly mismatched. The difference is called input offset current, and even with matched resistances a small offset voltage (different from the input offset voltage below) can be produced. This offset voltage can create offsets or drifting in the operational amplifier. Input offset This voltage, which is what is required across the op-amp's input terminals to drive the output voltage to zero. In the perfect amplifier, there would be no input offset voltage.
However, it exists in actual op-amps because of imperfections in the differential amplifier that constitutes the input stage of the vast majority of these devices. Input offset voltage creates two problems: First, due to the amplifier's high voltage gain, it virtually assures that the amplifier output will go into saturation if it is operated without negative feedback, even when the input terminals are wired together. Second, in a closed loop, negative feedback configuration, the input offset voltage is amplified along with the signal and this may pose a problem if high precision DC amplification is required or if the input signal is very small. Common-mode gain A perfect operational amplifier amplifies only the voltage difference between its two inputs, completely rejecting all voltages that are common to both. However, the differential input stage of an operational amplifier is never perfect, leading to the amplification of these common voltages to some degree.
The standard measure of this defect is called the (denoted CMRR). Minimization of common mode gain is usually important in non-inverting amplifiers (described below) that operate at high amplification. Power-supply rejection The output of a perfect operational amplifier will be completely independent from its power supply. Every real operational amplifier has a finite (PSRR) that reflects how well the op-amp can reject changes in its supply voltage. Temperature effects All parameters change with temperature. Temperature drift of the input offset voltage is especially important. Drift Real op-amp parameters are subject to slow change over time and with changes in temperature, input conditions, etc.
AC imperfections The op-amp gain calculated at DC does not apply at higher frequencies. Thus, for high-speed operation, more sophisticated considerations must be used in an op-amp circuit design. Finite All amplifiers have finite bandwidth. To a first approximation, the op-amp has the frequency response of an with gain. That is, the gain of a typical op-amp is inversely proportional to frequency and is characterized by its (GBWP). For example, an op-amp with a GBWP of 1 MHz would have a gain of 5 at 200 kHz, and a gain of 1 at 1 MHz.
This dynamic response coupled with the very high DC gain of the op-amp gives it the characteristics of a first-order with very high DC gain and low cutoff frequency given by the GBWP divided by the DC gain. The finite bandwidth of an op-amp can be the source of several problems, including: Stability Associated with the bandwidth limitation is a phase difference between the input signal and the amplifier output that can lead to in some feedback circuits. For example, a sinusoidal output signal meant to interfere destructively with an input signal of the same frequency will interfere constructively if delayed by 180 degrees forming.
In these cases, the feedback circuit can be by means of, which increases the of the open-loop circuit. The circuit designer can implement this compensation externally with a separate circuit component. Alternatively, the compensation can be implemented within the operational amplifier with the addition of a that sufficiently attenuates the high-frequency gain of the operational amplifier. The location of this pole may be fixed internally by the manufacturer or configured by the circuit designer using methods specific to the op-amp. In general, dominant-pole frequency compensation reduces the bandwidth of the op-amp even further. When the desired closed-loop gain is high, op-amp frequency compensation is often not needed because the requisite open-loop gain is sufficiently low; consequently, applications with high closed-loop gain can make use of op-amps with higher bandwidths. Distortion, and other effects Limited bandwidth also results in lower amounts of feedback at higher frequencies, producing higher distortion, and output impedance as the frequency increases.
Typical low-cost, general-purpose op-amps exhibit a GBWP of a few megahertz. Specialty and high-speed op-amps exist that can achieve a GBWP of hundreds of megahertz. For very high-frequency circuits, a is often used. Noise Amplifiers generate random voltage at the output even when there is no signal applied.
This can be due to thermal noise and flicker noise of the devices. For applications with high gain or high bandwidth, noise becomes a very important consideration. Input Most important for high frequency operation because it reduces input impedance and may cause phase shifts. Common-mode gain See DC imperfections, above. Power-supply rejection With increasing frequency the power-supply rejection usually gets worse. So it can be important to keep the supply clean of higher frequency ripples and signals, e.g. By the use of.
Non-linear imperfections. The input (yellow) and output (green) of a saturated op amp in an inverting amplifier Output voltage is limited to a minimum and maximum value close to the voltages. The output of older op-amps can reach to within one or two volts of the supply rails. The output of newer so-called 'rail to rail' op-amps can reach to within millivolts of the supply rails when providing low output currents. Slewing The amplifier's output voltage reaches its maximum rate of change, the, usually specified in volts per microsecond. When slewing occurs, further increases in the input signal have no effect on the rate of change of the output. Slewing is usually caused by the input stage saturating; the result is a constant current i driving a capacitance C in the amplifier (especially those capacitances used to implement its ); the slew rate is limited by d v/d t = i/ C.
Slewing is associated with the large-signal performance of an op-amp. Consider, for example, an op-amp configured for a gain of 10. Let the input be a 1 V, 100 kHz sawtooth wave.
That is, the amplitude is 1 V and the period is 10 microseconds. Accordingly, the rate of change (i.e., the slope) of the input is 0.1 V per microsecond. After 10× amplification, the output should be a 10 V, 100 kHz sawtooth, with a corresponding slew rate of 1 V per microsecond. However, the classic 741 op-amp has a 0.5 V per microsecond slew rate specification, so that its output can rise to no more than 5 V in the sawtooth's 10 microsecond period. Thus, if one were to measure the output, it would be a 5 V, 100 kHz sawtooth, rather than a 10 V, 100 kHz sawtooth. Modern high speed op-amps can have slew rates in excess of 5,000 V per microsecond.
However, it is more common for op-amps to have slew rates in the range 5–100 V per microsecond. For example, the general purpose TL081 op-amp has a slew rate of 13 V per microsecond. As a general rule, low power and small bandwidth op-amps have low slew rates.
As an example, the LT1494 micropower op-amp consumes 1.5 microamp but has a 2.7 kHz gain-bandwidth product and a 0.001 V per microsecond slew rate. Non- input-output relationship The output voltage may not be accurately proportional to the difference between the input voltages.
It is commonly called distortion when the input signal is a waveform. This effect will be very small in a practical circuit where substantial negative feedback is used. Phase reversal In some integrated op-amps, when the published common mode voltage is violated (e.g., by one of the inputs being driven to one of the supply voltages), the output may slew to the opposite polarity from what is expected in normal operation.
Under such conditions, negative feedback becomes positive, likely causing the circuit to 'lock up' in that state. Power considerations Limited The output current must be finite. In practice, most op-amps are designed to limit the output current so as not to exceed a specified level – around 25 mA for a type 741 IC op-amp – thus protecting the op-amp and associated circuitry from damage.
Modern designs are electronically more rugged than earlier implementations and some can sustain direct on their outputs without damage. Output sink current The output sink current is the maximum current allowed to sink into the output stage. Some manufacturers show the output voltage vs. The output sink current plot, which gives an idea of the output voltage when it is sinking current from another source into the output pin.
Limited dissipated The output current flows through the op-amp's internal output impedance, generating heat which must be dissipated. If the op-amp dissipates too much power, then its temperature will increase above some safe limit. The op-amp may enter thermal shutdown, or it may be destroyed. Modern integrated or op-amps approximate more closely the ideal op-amp than bipolar ICs when it comes to input impedance and input bias currents. Bipolars are generally better when it comes to input voltage offset, and often have lower noise. Generally, at room temperature, with a fairly large signal, and limited bandwidth, FET and MOSFET op-amps now offer better performance.
Internal circuitry of 741-type op-amp. A component-level diagram of the common 741 op-amp. Dotted lines outline:;; gain stage; voltage level shifter; output stage. Sourced by many manufacturers, and in multiple similar products, an example of a bipolar transistor operational amplifier is the 741 integrated circuit designed in 1968 by David Fullagar at after 's LM301 integrated circuit design.
In this discussion, we use the parameters of the to characterize the small-signal, grounded emitter characteristics of a transistor. In this model, the current gain of a transistor is denoted h fe, more commonly called the β. Architecture A small-scale, the 741 op-amp shares with most op-amps an internal structure consisting of three gain stages:. (outlined ) — provides high differential amplification (gain), with rejection of common-mode signal, low noise, high, and drives a. Voltage amplifier (outlined ) — provides high voltage gain, a single-pole frequency, and in turn drives the. Output amplifier (outlined and ) — provides high current gain (low ), along with output current limiting, and output short-circuit protection.
Additionally, it contains (outlined red) bias circuitry and capacitor (30 pF). Differential amplifier The input stage consists of a cascaded (outlined in ) followed by a current-mirror. This constitutes a, turning a differential voltage signal at the bases of Q1, Q2 into a current signal into the base of Q15.
It entails two cascaded transistor pairs, satisfying conflicting requirements. The first stage consists of the matched NPN pair Q1, Q2 that provide high input impedance.
The second is the matched PNP pair Q3, Q4 that eliminates the undesirable; it drives an Q7 plus matched pair Q5, Q6. That active load is implemented as a modified; its role is to convert the (differential) input current signal to a single-ended signal without the attendant 50% losses (increasing the op-amp's open-loop gain by 3 dB). Thus, a small-signal differential current in Q3 versus Q4 appears summed (doubled) at the base of Q15, the input of the voltage gain stage.
Voltage amplifier The voltage gain stage (outlined in ) consists of the two NPN transistors Q15/Q19 connected in a and uses the output side of current mirror Q12/Q13 as its collector (dynamic) load to achieve its high voltage gain. The output sink transistor Q20 receives its base drive from the common collectors of Q15 and Q19; the level-shifter Q16 provides base drive for the output source transistor Q14. The transistor Q22 prevents this stage from delivering excessive current to Q20 and thus limits the output sink current.
Output amplifier The output stage (Q14, Q20, outlined in ) is a complementary-symmetry amplifier. It provides an output drive with impedance of ≈50Ω, in essence, current gain. Transistor Q16 (outlined in ) provides the quiescent current for the output transistors, and Q17 provides output current limiting. Biasing circuits Provide appropriate quiescent current for each stage of the op-amp. The resistor (39 kΩ) connecting the (diode-connected) Q11 and Q12, and the given supply voltage ( V S+ − V S−), determine the current in the, (matched pairs) Q10/Q11 and Q12/Q13.
The collector current of Q11, i 11 × 39 kΩ = V S+ − V S− − 2 V BE. For the typical V S = ±20 V, the standing current in Q11/Q12 (as well as in Q13) would be 1 mA. A supply current for a typical 741 of about 2 mA agrees with the notion that these two bias currents dominate the quiescent supply current.
Transistors Q11 and Q10 form a, with quiescent current in Q10 i 10 such that ln( i 11 / i 10) = i 10 × 5 kΩ / 28 mV, where 5 kΩ represents the emitter resistor of Q10, and 28 mV is V T, the at room temperature. In this case i 10 ≈ 20 μA. Differential amplifier The biasing circuit of this stage is set by a feedback loop that forces the collector currents of Q10 and Q9 to (nearly) match. The small difference in these currents provides the drive for the common base of Q3/Q4 (note that the base drive for input transistors Q1/Q2 is the input bias current and must be sourced externally). The summed quiescent currents of Q1/Q3 plus Q2/Q4 is mirrored from Q8 into Q9, where it is summed with the collector current in Q10, the result being applied to the bases of Q3/Q4. The quiescent currents of Q1/Q3 (resp., Q2/Q4) i 1 will thus be half of i 10, of order 10 μA.
Input bias current for the base of Q1 (resp. Q2) will amount to i 1 / β; typically 50 nA, implying a current gain h fe ≈ 200 for Q1(Q2). This feedback circuit tends to draw the common base node of Q3/Q4 to a voltage V com − 2 V BE, where V com is the input common-mode voltage. At the same time, the magnitude of the quiescent current is relatively insensitive to the characteristics of the components Q1–Q4, such as h fe, that would otherwise cause temperature dependence or part-to-part variations. Transistor Q7 drives Q5 and Q6 into conduction until their (equal) collector currents match that of Q1/Q3 and Q2/Q4. The quiescent current in Q7 is V BE / 50 kΩ, about 35 μA, as is the quiescent current in Q15, with its matching operating point. Thus, the quiescent currents are pairwise matched in Q1/Q2, Q3/Q4, Q5/Q6, and Q7/Q15.
Voltage amplifier Quiescent currents in Q16 and Q19 are set by the current mirror Q12/Q13, which is running at 1 mA. Through some mechanism, the collector current in Q19 tracks that standing current. Output amplifier In the circuit involving Q16 (variously named or V BE multiplier), the 4.5 kΩ resistor must be conducting about 100 μA, with the Q16 V BE roughly 700 mV. Then the V CB must be about 0.45 V and V CE at about 1.0 V. Because the Q16 collector is driven by a current source and the Q16 emitter drives into the Q19 collector current sink, the Q16 transistor establishes a voltage difference between Q14 base and Q20 base of 1 V, regardless of the common-mode voltage of Q14/Q20 base.
The standing current in Q14/Q20 will be a factor smaller than the 1 mA quiescent current in the class A portion of the op amp. This (small) standing current in the output transistors establishes the output stage in class AB operation and reduces the of this stage. Small-signal differential mode A small differential input voltage signal gives rise, through multiple stages of current amplification, to a much larger voltage signal on output. Input impedance The input stage with Q1 and Q3 is similar to an emitter-coupled pair (long-tailed pair), with Q2 and Q4 adding some degenerating impedance. The input impedance is relatively high because of the small current through Q1-Q4.
A typical 741 op amp has a differential input impedance of about 2 MΩ. The common mode input impedance is even higher, as the input stage works at an essentially constant current. Differential amplifier A differential voltage V In at the op-amp inputs (pins 3 and 2, respectively) gives rise to a small differential current in the bases of Q1 and Q2 i In ≈ V In / (2 h ie × h fe). This differential base current causes a change in the differential collector current in each leg by i In × h fe. Introducing the transconductance of Q1, g m = h fe / h ie, the (small-signal) current at the base of Q15 (the input of the voltage gain stage) is V In × g m / 2.
This portion of the op amp cleverly changes a differential signal at the op amp inputs to a single-ended signal at the base of Q15, and in a way that avoids wastefully discarding the signal in either leg. To see how, notice that a small negative change in voltage at the inverting input (Q2 base) drives it out of conduction, and this incremental decrease in current passes directly from Q4 collector to its emitter, resulting in a decrease in base drive for Q15.
On the other hand, a small positive change in voltage at the non-inverting input (Q1 base) drives this transistor into conduction, reflected in an increase in current at the collector of Q3. This current drives Q7 further into conduction, which turns on current mirror Q5/Q6. Thus, the increase in Q3 emitter current is mirrored in an increase in Q6 collector current; the increased collector currents shunts more from the collector node and results in a decrease in base drive current for Q15. Besides avoiding wasting 3 dB of gain here, this technique decreases common-mode gain and feedthrough of power supply noise.
Voltage amplifier A current signal i at Q15's base gives rise to a current in Q19 of order i × β 2 (the product of the h fe of each of Q15 and Q19, which are connected in a ). This current signal develops a voltage at the bases of output transistors Q14/Q20 proportional to the h ie of the respective transistor. Output amplifier Output transistors Q14 and Q20 are each configured as an emitter follower, so no voltage gain occurs there; instead, this stage provides current gain, equal to the h fe of Q14 (resp.
The output impedance is not zero, as it would be in an ideal op-amp, but with negative feedback it approaches zero at low frequencies. Overall open-loop voltage gain The net open-loop small-signal voltage gain of the op amp involves the product of the current gain h fe of some 4 transistors. In practice, the voltage gain for a typical 741-style op amp is of order 200,000, and the current gain, the ratio of input impedance (≈2−6 MΩ) to output impedance (≈50Ω) provides yet more (power) gain. Other linear characteristics Small-signal common mode gain The ideal op amp has infinite, or zero common-mode gain.
In the present circuit, if the input voltages change in the same direction, the negative feedback makes Q3/Q4 base voltage follow (with 2 V BE below) the input voltage variations. Now the output part (Q10) of Q10-Q11 current mirror keeps up the common current through Q9/Q8 constant in spite of varying voltage.
Q3/Q4 collector currents, and accordingly the output current at the base of Q15, remain unchanged. In the typical 741 op amp, the common-mode rejection ratio is 90 dB, implying an open-loop common-mode voltage gain of about 6. Frequency compensation The innovation of the Fairchild μA741 was the introduction of via an on-chip (monolithic) capacitor, simplifying application of the op amp by eliminating the need for external components for this function. The 30 pF capacitor stabilizes the amplifier via and functions in a manner similar to an op-amp circuit. Also known as 'dominant compensation' because it introduces a pole that masks (dominates) the effects of other poles into the frequency response; in a 741 op amp this pole can be as low as 10 Hz (where it causes a −3 dB loss of open loop voltage gain). This internal compensation is provided to achieve unconditional of the amplifier in negative feedback configurations where the feedback network is non-reactive and the gain is or higher. By contrast, amplifiers requiring external compensation, such as the μA748, may require external compensation or closed-loop gains significantly higher than unity.
Input offset voltage The 'offset null' pins may be used to place external resistors (typically in the form of the two ends of a potentiometer, with the slider connected to V S–) in parallel with the emitter resistors of Q5 and Q6, to adjust the balance of the Q5/Q6 current mirror. The potentiometer is adjusted such that the output is null (midrange) when the inputs are shorted together.
Non-linear characteristics Input breakdown voltage The transistors Q3, Q4 help to increase the reverse V BE rating: the base-emitter junctions of the NPN transistors Q1 and Q2 break down at around 7V, but the PNP transistors Q3 and Q4 have V BE breakdown voltages around 50 V. Output-stage voltage swing and current limiting Variations in the quiescent current with temperature, or between parts with the same type number, are common, so and may be subject to significant variation. The output range of the amplifier is about one volt less than the supply voltage, owing in part to V BE of the output transistors Q14 and Q20. The 25 Ω resistor at the Q14 emitter, along with Q17, acts to limit Q14 current to about 25 mA; otherwise, Q17 conducts no current. Current limiting for Q20 is performed in the voltage gain stage: Q22 senses the voltage across Q19's emitter resistor (50Ω); as it turns on, it diminishes the drive current to Q15 base. Later versions of this amplifier schematic may show a somewhat different method of output current limiting. Applicability considerations While the 741 was historically used in audio and other sensitive equipment, such use is now rare because of the improved performance of more modern op-amps.
Apart from generating noticeable hiss, 741s and other older op-amps may have poor and so will often introduce cable-borne mains hum and other common-mode interference, such as switch 'clicks', into sensitive equipment. The '741' has come to often mean a generic op-amp IC (such as μA741, LM301, 558, LM324, TBA221 — or a more modern replacement such as the TL071). The description of the 741 output stage is qualitatively similar for many other designs (that may have quite different input stages), except:. Some devices (μA748, LM301, LM308) are not internally compensated (require an external capacitor from output to some point within the operational amplifier, if used in low closed-loop gain applications). Some modern devices have 'rail-to-rail output' capability, meaning that the output can range from within a few millivolts of the positive supply voltage to within a few millivolts of the negative supply voltage. Classification Op-amps may be classified by their construction:.
discrete (built from individual or ). IC (fabricated in an ) — most common. hybrid IC op-amps may be classified in many ways, including:. Military, Industrial, or Commercial grade (for example: the LM301 is the commercial grade version of the LM101, the LM201 is the industrial version). This may define ranges and other environmental or quality factors.
Classification by package type may also affect environmental hardiness, as well as manufacturing options;, and other through-hole packages are tending to be replaced. Classification by internal compensation: op-amps may suffer from high frequency in some circuits unless a small compensation capacitor modifies the phase and frequency responses. Op-amps with a built-in capacitor are termed ' compensated', and allow circuits above some specified gain to operate stably with no external capacitor. In particular, op-amps that are stable even with a closed loop gain of 1 are called 'unity gain compensated'.
Single, dual and quad versions of many commercial op-amp IC are available, meaning 1, 2 or 4 operational amplifiers are included in the same package. Rail-to-rail input (and/or output) op-amps can work with input (and/or output) signals very close to the power supply rails. op-amps (such as the CA3140E) provide extremely high input resistances, higher than -input op-amps, which are normally higher than -input op-amps. other varieties of op-amp include programmable op-amps (simply meaning the quiescent current, bandwidth and so on can be adjusted by an external resistor). manufacturers often tabulate their op-amps according to purpose, such as low-noise pre-amplifiers, wide bandwidth amplifiers, and so on.
Applications. Main article: Use in electronics system design The use of op-amps as circuit blocks is much easier and clearer than specifying all their individual circuit elements (transistors, resistors, etc.), whether the amplifiers used are integrated or discrete circuits. In the first approximation op-amps can be used as if they were ideal differential gain blocks; at a later stage limits can be placed on the acceptable range of parameters for each op-amp. Circuit design follows the same lines for all electronic circuits.
A specification is drawn up governing what the circuit is required to do, with allowable limits. For example, the gain may be required to be 100 times, with a tolerance of 5% but drift of less than 1% in a specified temperature range; the input impedance not less than one megohm; etc. A basic is designed, often with the help of circuit modeling (on a computer). Specific commercially available op-amps and other components are then chosen that meet the design criteria within the specified tolerances at acceptable cost.
If not all criteria can be met, the specification may need to be modified. A prototype is then built and tested; changes to meet or improve the specification, alter functionality, or reduce the cost, may be made. Applications without using any feedback That is, the op-amp is being used as a.
Note that a device designed primarily as a comparator may be better if, for instance, speed is important or a wide range of input voltages may be found, since such devices can quickly recover from full on or full off ('saturated') states. A voltage level detector can be obtained if a reference voltage V ref is applied to one of the op-amp's inputs. This means that the op-amp is set up as a comparator to detect a positive voltage. If the voltage to be sensed, E i, is applied to op amp's (+) input, the result is a noninverting positive-level detector: when E i is above V ref, V O equals + V sat; when E i is below V ref, V O equals − V sat. If E i is applied to the inverting input, the circuit is an inverting positive-level detector: When E i is above V ref, V O equals − V sat. A zero voltage level detector ( E i = 0) can convert, for example, the output of a sine-wave from a function generator into a variable-frequency square wave.
If E i is a sine wave, triangular wave, or wave of any other shape that is symmetrical around zero, the zero-crossing detector's output will be square. Zero-crossing detection may also be useful in triggering at the best time to reduce mains interference and current spikes. Positive-feedback applications. Schmitt trigger implemented by a non-inverting comparator Another typical configuration of op-amps is with positive feedback, which takes a fraction of the output signal back to the non-inverting input. An important application of it is the comparator with hysteresis, the.
Some circuits may use positive feedback and negative feedback around the same amplifier, for example. Because of the wide slew range and lack of positive feedback, the response of all the open-loop level detectors described will be relatively slow. External overall positive feedback may be applied, but (unlike internal positive feedback that may be applied within the latter stages of a purpose-designed comparator) this markedly affects the accuracy of the zero-crossing detection point. Using a general-purpose op-amp, for example, the frequency of E i for the sine to square wave converter should probably be below 100 Hz. Negative-feedback applications Non-inverting amplifier. GAP/R's K2-W: a vacuum-tube op-amp (1953) 1947: An op-amp with an explicit non-inverting input. In 1947, the operational amplifier was first formally defined and named in a paper by of Columbia University.
In this same paper a footnote mentioned an op-amp design by a student that would turn out to be quite significant. This op-amp, designed by, was superior in a variety of ways. It had two major innovations.
Its input stage used a long-tailed pair with loads matched to reduce drift in the output and, far more importantly, it was the first op-amp design to have two inputs (one inverting, the other non-inverting). The differential input made a whole range of new functionality possible, but it would not be used for a long time due to the rise of the chopper-stabilized amplifier. 1949: A chopper-stabilized op-amp.
In 1949, Edwin A. Goldberg designed a -stabilized op-amp.
This set-up uses a normal op-amp with an additional amplifier that goes alongside the op-amp. The chopper gets an AC signal from by switching between the DC voltage and ground at a fast rate (60 Hz or 400 Hz). This signal is then amplified, rectified, filtered and fed into the op-amp's non-inverting input. This vastly improved the gain of the op-amp while significantly reducing the output drift and DC offset. Unfortunately, any design that used a chopper couldn't use their non-inverting input for any other purpose. Nevertheless, the much improved characteristics of the chopper-stabilized op-amp made it the dominant way to use op-amps.
Techniques that used the non-inverting input regularly would not be very popular until the 1960s when op-amp started to show up in the field. 1953: A commercially available op-amp. In 1953, vacuum tube op-amps became commercially available with the release of the model K2-W from Researches, Incorporated. The designation on the devices shown, GAP/R, is an acronym for the complete company name. Two nine-pin vacuum tubes were mounted in an octal package and had a model K2-P chopper add-on available that would effectively 'use up' the non-inverting input. This op-amp was based on a descendant of Loebe Julie's 1947 design and, along with its successors, would start the widespread use of op-amps in industry.
GAP/R's model P45: a solid-state, discrete op-amp (1961). 1961: A discrete IC op-amp. With the birth of the in 1947, and the silicon transistor in 1954, the concept of ICs became a reality.
The introduction of the in 1959 made transistors and ICs stable enough to be commercially useful. By 1961, solid-state, discrete op-amps were being produced. These op-amps were effectively small circuit boards with packages such as. They usually had hand-selected resistors in order to improve things such as voltage offset and drift.
The P45 (1961) had a gain of 94 dB and ran on ±15 V rails. It was intended to deal with signals in the range of ±10 V. 1961: A varactor bridge op-amp. There have been many different directions taken in op-amp design.
Bridge op-amps started to be produced in the early 1960s. They were designed to have extremely small input current and are still amongst the best op-amps available in terms of common-mode rejection with the ability to correctly deal with hundreds of volts at their inputs. GAP/R's model PP65: a solid-state op-amp in a potted module (1962) 1962: An op-amp in a potted module.
By 1962, several companies were producing modular potted packages that could be plugged into. These packages were crucially important as they made the operational amplifier into a single which could be easily treated as a component in a larger circuit. 1963: A monolithic IC op-amp.
In 1963, the first monolithic IC op-amp, the μA702 designed by at Fairchild Semiconductor, was released. Monolithic consist of a single chip as opposed to a chip and discrete parts (a discrete IC) or multiple chips bonded and connected on a circuit board (a hybrid IC). Almost all modern op-amps are monolithic ICs; however, this first IC did not meet with much success. Issues such as an uneven supply voltage, low gain and a small dynamic range held off the dominance of monolithic op-amps until 1965 when the μA709 (also designed by Bob Widlar) was released.
1968: Release of the μA741. The popularity of monolithic op-amps was further improved upon the release of the LM101 in 1967, which solved a variety of issues, and the subsequent release of the μA741 in 1968. The μA741 was extremely similar to the LM101 except that Fairchild's facilities allowed them to include a 30 pF compensation capacitor inside the chip instead of requiring external compensation. This simple difference has made the 741 the canonical op-amp and many modern amps base their pinout on the 741s. The μA741 is still in production, and has become ubiquitous in electronics—many manufacturers produce a version of this classic chip, recognizable by part numbers containing 741.
The same part is manufactured by several companies. 1970: First high-speed, low-input current FET design. In the 1970s high speed, low-input current designs started to be made by using. These would be largely replaced by op-amps made with in the 1980s. ADI's HOS-050: a high speed hybrid IC op-amp (1979) 1972: Single sided supply op-amps being produced. A single sided supply op-amp is one where the input and output voltages can be as low as the negative power supply voltage instead of needing to be at least two volts above it. The result is that it can operate in many applications with the negative supply pin on the op-amp being connected to the signal ground, thus eliminating the need for a separate negative power supply.
The LM324 (released in 1972) was one such op-amp that came in a quad package (four separate op-amps in one package) and became an industry standard. In addition to packaging multiple op-amps in a single package, the 1970s also saw the birth of op-amps in hybrid packages. These op-amps were generally improved versions of existing monolithic op-amps. As the properties of monolithic op-amps improved, the more complex hybrid ICs were quickly relegated to systems that are required to have extremely long service lives or other specialty systems. An op-amp in a mini DIP package Recent trends. Recently supply voltages in analog circuits have decreased (as they have in digital logic) and low-voltage op-amps have been introduced reflecting this.
Supplies of 5 V and increasingly 3.3 V (sometimes as low as 1.8 V) are common. To maximize the signal range modern op-amps commonly have rail-to-rail output (the output signal can range from the lowest supply voltage to the highest) and sometimes rail-to-rail inputs. Recent 'boomer' amplifiers such as the LM4871 and 8002 also have a shutdown feature, an internal power supply for biasing, and a bypass pin to connect a bypass capacitor for that power supply.
See also. This definition hews to the convention of measuring op-amp parameters with respect to the zero voltage point in the circuit, which is usually half the total voltage between the amplifier's positive and negative power rails. Many older designs of operational amplifiers have offset null inputs to allow the offset to be manually adjusted away.
Modern precision op-amps can have internal circuits that automatically cancel this offset using or other circuits that measure the offset voltage periodically and subtract it from the input voltage. That the output cannot reach the power supply voltages is usually the result of limitations of the amplifier's output stage transistors. Widlar used this same trick in μA702 and μA709 References.
2007-06-26 at the – Retrieved November 10, 2007. From the original on 1 January 2016. Retrieved 8 November 2015.
APEX PA98 Op Amp Modules, Selling Price: $207.51. Jacob Millman, Microelectronics: Digital and Analog Circuits and Systems, McGraw-Hill, 1979, pp.
(PDF) from the original on 2016-12-27. (PDF) from the original on 2016-11-23. ^ Horowitz, Paul; Hill, Winfield (1989). Cambridge, UK: Cambridge University Press. Stout Handbook of Operational Amplifier Circuit Design (McGraw-Hill, 1976, ) pp. 1–11.
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(PDF) from the original on October 24, 2012Handout #18: EE214 Fall 2002. Lu, Liang-Hung. National Taiwan University, Graduate Institute of Electronics Engineering. (PDF) from the original on 2014-02-24. Retrieved 2014-02-22. From the original on 9 October 2017. Retrieved 28 April 2018.
An input bias current of 1 µA through a DC source resistance of 10 kΩ produces a 10 mV offset voltage. If the other input bias current is the same and sees the same source resistance, then the two input offset voltages will cancel out. Balancing the DC source resistances may not be necessary if the input bias current and source resistance product is small. ^ Jung, Walter G. 'Chapter 8: Op Amp History'. Retrieved 2008-11-15.; Randall, Robert H.; Russell, Frederick A.
Proceedings of the IRE. 35 (5): 444–452. (PDF) from the original on 2012-10-07.
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Further reading. Op Amps For Everyone; 5th Ed; Bruce Carter and Ron Mancini; Newnes; 484 pages; 2017;. Operational Amplifiers - Theory and Design; 3rd Ed; Johan Huijsing; Springer; 423 pages; 2017;.; 3rd Ed; James Fiore; 589 pages; 2016;. Analysis and Design of Linear Circuits; 8th Ed; Roland Thomas, Albert Rosa, Gregory Toussaint; Wiley; 912 pages; 2016;. Design with Operational Amplifiers and Analog Integrated Circuits; 4th Ed; Sergio Franco; McGraw Hill; 672 pages; 2015;. Small Signal Audio Design; 2nd Ed; Douglas Self; Focal Press; 780 pages; 2014;. Linear Circuit Design Handbook; 1st Ed; Hank Zumbahlen; Newnes; 960 pages; 2008;.
Op Amp Applications Handbook; 1st Ed;; Newnes; 896 pages; 2005;. Operational Amplifiers and Linear Integrated Circuits; 6th Ed; Robert Coughlin and Frederick Driscoll; Prentice Hall; 529 pages; 2001;. Active-Filter Cookbook; 2nd Ed;; Sams; 240 pages; 1996;. IC Op-Amp Cookbook; 3rd Ed;; Prentice Hall; 433 pages; 1986;. Engineer's Mini-Notebook – OpAmp IC Circuits; 1st Ed; III; Radio Shack; 49 pages; 1985; ASIN B000DZG196. Applications of Operational Amplifiers - Third Generation Techniques; 1st Ed; Jerald Graeme; & McGraw Hill; 233 pages; 1973; LSN 0-07-023890-1. Books with OpAmp chapters.
Learning the Art of Electronics - A Hands-On Lab Course; 1st Ed; Thomas Hayes and; 1150 pages; 2016;. (Part 3 is 268 pages).; 3rd Ed; and Winfield Hill; 1220 pages; 2015;. (Chapter 4 is 69 pages). Volume III - Semiconductors; 5th Ed; Tony Kuphaldt; 528 page; 2009.
(Chapter 8 is 59 pages). Troubleshooting Analog Circuits; 1st Ed;; Newnes; 217 pages; 1991;. (Chapter 8 is 19 pages). Analog Applications Manual; 1st Ed;; 418 pages; 1979. (Chapter 3 is 32 pages) External links Wikimedia Commons has media related to.
Wikiversity has learning resources about The Wikibook has a page on the topic of:. National Semiconductor Corporation. Chapter on All About Circuits.
Introduction to loop gain, gain and phase margin, loop stability. How to measure offset voltage, offset and bias current, gain, CMRR, and PSRR.
Introductory on-line text by E. Mastascusa. using spot noise. from vacuum tubes to about 2002.
Lots of detail, with schematics. IC part is somewhat ADI-centric. by. – A free repository of materials from George A Philbrick / Researches - Operational Amplifier Pioneer., Electronic Design Magazine Datasheets / Databooks.
(NE5534 is similar single). (TL074 is Quad).
Operational Amplifier By Ramakant Gaikwad Pdf Reader Rating: 3,4/5 7911reviews Download Read Op-amps and Linear Integrated Circuit Technology PDF books PDF Free Download Here This accurate and easy-to-understand book presents readers with the basic principles of operational amplifiers and integrated circuits—with a very practical approach. A large number of examples, questions, problems, and practical circuit applications make it a valuable reference guide. Chapter topics include an introduction to, frequency response and negative feedback of op-amps—along with interpretation of data sheets and characteristics. Also covered are active filters and oscillators, comparators and converters, specialized IC applications and system projects.For professional design engineers, technologists, and technicians, with self-study interests, who need the ability to adapt to changing technology as new devices appear on the market. Operational amplifier circuit manual, Robert J. Traister, 1989.
Descargar Gratis Libros Barco De Vapor Editorial. Operational Amplifiers and Linear Integrated Circuits, 1998. Op-amps and linear integrated circuit technology, Ramakant A. Gayakwad, 1983, Technology.
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