What is Operational amplifier: Definition and 48 Discussions

An operational amplifier (often op amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In this configuration, an op amp produces an output potential (relative to circuit ground) that is typically 100,000 times larger than the potential difference between its input terminals. Operational amplifiers had their origins in analog computers, where they were used to perform mathematical operations in linear, non-linear, and frequency-dependent circuits.
The popularity of the op amp as a building block in analog circuits is due to its versatility. By using negative feedback, the characteristics of an op-amp circuit, its gain, input and output impedance, bandwidth etc. are determined by external components and have little dependence on temperature coefficients or engineering tolerance in the op amp itself.
Op amps are used widely in electronic devices today, including a vast array of consumer, industrial, and scientific devices. Many standard IC op amps cost only a few cents; however, some integrated or hybrid operational amplifiers with special performance specifications may cost over US$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 differential amplifier. Other types of differential amplifier include the fully differential amplifier (similar to the op amp, but with two outputs), the instrumentation amplifier (usually built from three op amps), the isolation amplifier (similar to the instrumentation amplifier, but with tolerance to common-mode voltages that would destroy an ordinary op amp), and negative-feedback amplifier (usually built from one or more op amps and a resistive feedback network).

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  1. ZoeDale

    Engineering Analyzing this operational amplifier circuit with DC

    Hi all, I attached my attempt at a solution in the attached picture. I am using the textbook titiled as ”electronic circuit analysis“ by David E. Johnson, and op amp is in chap 3; while I did not find any example that attach the Vee and Vcc with amplifier . It seems that v+ = v- doesn’t hold in...
  2. Jason-Li

    Operational Amplifiers & Resistors to form a Black Box

    So basically I am trying to give an output of Vo = 10(V2-V1) From Figure 9 Example Gain of first Op Amp = Rf / R1, if R1 & R2 are equal. What's throwing me off is using 5 resistors to create a circuit rather than 6 or just 3. My initial thoughts were the following: To use the first loop...
  3. N

    Operational Amplifier key parameters

    << Mentor Note -- new poster has been reminded to show their work on schoolwork-type problems >>
  4. bobg123

    Engineering Circuit input impedance with ground in an OP Amp circuit

    I've been given the following circuit and have been asked to find the input impedance and the impedance between the input terminal and ground. I've never encountered an operational amplifier configured like this. I know that the voltages at the - and + terminals of the op amp are ideally equal...
  5. maven sharma

    Integrating operational amplifier

    Homework Statement Calculate the output voltage of the amplifier 2. Homework Equations [/B] https://www.electronics-tutorials.ws/opamp/opamp32.gif The Attempt at a Solution I do not know how to approach a circuit with RC in series to inverting terminal of integrating op amp

    How can I plot a graph for these opamp results?

    i have build and simulated the op amp circuit, i have recorded the voltage gain at different frequencies, now i need to plot a graph for the two results in same graph paper, i have not plotted a graph before for the related task so i need to understand from the basics, i need some one to...
  7. A

    Window Comparator: Understanding the Output Behavior and Common Errors

    So I've been reading an intro book to electronics and I got to a section about operational amplifiers. It talks about different uses of them and how they can be used as comparators. It then talks about a specific comparator called a window comparator which will output a positive voltage if the...
  8. A

    What are the values of Rf and V2 for the given circuit?

    Homework Statement Hello, I am trying to Calculate The Resistance Rf and the value of the Voltage V2. The setup is a logarithmic Op amp connected to a differential Op amp. Both Op amps obey the Golden Rules. Attached below is my attempt at the solution and the question. Currently, I have an...
  9. O

    What is the relationship between frequency range and GBW in amplifiers?

    I have an op-amp with frequency range 20Hz - 20kHz. Is frequency range the same as bandwidth?
  10. Z

    Increasing voltage using operational amplifier

    I want to build own circuit usinghttps://ez.analog.com/external-link.jspa?url=http%3A%2F%2Fwww.kynix.com%2FProduct%2FCate%2F470.htmland resistors. I have 12V power source (car accumulator) and 6V input voltage (Vin). I want to get 12V Vout and 25W at the output. So that is about 2A...
  11. T

    Operational Amplifier Comparator Circuit

    Homework Statement The variation with time t of the potential Vin at the inverting input of the op-amp is shown in Fig. 10.2. On the axes of Fig. 10.2, draw the variation with time t of the output potential of the op-amp. (pictures attached) Homework Equations The potential divider equation to...
  12. A

    Operational Amplifier Homework Question

    Homework Statement What is the value of V2 in terms of Vos? Homework EquationsThe Attempt at a Solution In the class, we were told that this is just a non-inverting amplifier, thus V2= Vos x (R2/R1+R2). However, I want to work out the solution by applying nullator hypothesis (voltage...
  13. T

    Operational amplifier with feedback problem

    Homework Statement Homework EquationsThe Attempt at a Solution [/B] Using the equations above, I'm not getting the right answer for beta which is 0.4926 V/A. Is my model wrong ?
  14. C

    Engineering Transimpedance Operational Amplifier Simulation circuit help

    Homework Statement (a) Derive the relationship between the output voltage V and the input current I; i.e. if V = kI find k in terms of R1, R2 and Rf. (b) Calculate the current I if Rf = 10 MΩ, R1 = 90 kΩ, R2 = 10 kΩ and V –0.1 V. (c) Model the circuit using PSPICE [using an ideal opamp] and...
  15. P

    Can you help with operational amplifier homework?

    Homework Statement Good morning everybody,I'm french and my english isn't good but I need help for this exercice please: I tried to do this exercice,however I'm not sure of my answers,can you tell me if they are good , or what mistakes I committed ? Here the exercice : 2. Revelant equations...
  16. G

    How can I generate a negative supply voltage for an Opamp?

    Hello. I really don't get a concept of a way to generates negative voltage as a one of the supply voltage to typical OP-AMP. (Operational Amplifier) The output voltages is supposed to swing to more than 10 V thus supply voltages to OP-AMP should be +15V and -15V. I'm thinking of supply these...
  17. T

    Op-amp: Current and bandwidth question

    Does current flow through the feedback resistor without going through the op-amp at all? After all, the op-amp is supposed to have very high input impedance right, so if the current just flows through the feedback resistor, wouldn't there be nothing going through the op-amp? Also, how does the...
  18. dwn

    Engineering Understanding Source Transformations in Operational Amplifier Circuits

    Homework Statement See ImageHomework Equations Source Transformations The Attempt at a Solution The answer is given, but I do not understand how they got it. When I multiply 9mA and 947.308Ω resistor, I get 8.526...what am I doing wrong? Also, could someone explain how they went on to get...
  19. P

    What are the internal mechanisms of the 741 Operational Amplifier?

    Hello, As I mentioned before, thank you for all the mentoring. It has been a huge help to my understanding. So, I am trying to stay one - two weeks ahead of my operational amplifiers class. I know that we will soon be discussing the 741 Operational amplifier. While reading about it, I...
  20. A

    Finding V(out) of Operational Amplifier

    Homework Statement Op Amp powered from +-20V DC. Find V(out) in Volts. All Resistances/Batteries given. http://imageshack.us/a/img805/2803/photoup.png Help would be much appreciated
  21. R

    Need help with transconductance operational amplifier

    Hi all, Does anyone know how do I connect an OTA if I want to use it as a voltage-controlled current source, meaning that it will ouput an AC current when i supplied an AC voltage? Any guide I can refer to? And how do I adjust the gain or transconductance, gm? For example, OPA860 with...
  22. M

    Instrument amplifier or just operational amplifier?

    Hi: i have a project to design ECG system: read ECG signal by using (DAQ)data aquestion and the Signal processing(bandpass& notch filter) will be done by using MATLAB program. I was Intended to use instrument amplifier to obtain I,II or III signals as this figure: but my supervisor...
  23. S

    Deriving Vout in an inverting operational amplifier.

    Pls does anyone know how to derive for Vout1 and Vout3 in terms of Va and Vb for an inverting operational amplifier. Thank you.
  24. C

    Why does negative feedback stabilize an operational amplifier?

    I'm studying for an exam and I'm struggling to understand op amps, here's my problem: I understand that for an op amp to have a controllable gain, the difference between the input terminals must be very very close to zero (and you can assume it is zero). And to do this you use negative...
  25. Y

    Operational Amplifier Circuit for Adding AC & DC Signals

    I need a circuit that adds an AC signal with magnitude of 25mV and a variable DC signal between 0 to 5V, and applies it to a diode.
  26. L

    Problem on Operational Amplifier

    Hi, Just I really short question. I have attached my assignment as a picture file. Don't worry I am not asking you to give me a solution. I just want to know, in the question it tells us that there is a internal resistance of 1MΩ, and a supply voltage of 10V. I am really confuse, as all...
  27. G

    Inverting operational amplifier circuit won't work

    I'm making a simple circuit on the breadboard with a 741 op amp. The feedback resistor is 150 kohms, and the input resistor is 100 kilo ohms, means the gain is 1.5. The input voltage is about 5.33. The power supply is ±18 V. For some reason the output voltage is 0.98 V instead of the amplified...
  28. Femme_physics

    Operational Amplifier Output Voltage with Equal Resistors

    Homework Statement http://img51.imageshack.us/img51/1912/vout.jpg Given the supply voltages of the operational amplifier are (plus and minus)15V, as well it is given that R1 = R2 = R3. We get that Vout is -15V True or false? Explain.The Attempt at a Solution [SIZE="5"]False because it...
  29. S

    Operational amplifier exam questions

    Homework Statement See attached file for relevant questions. I'm finding the Op-amp questions in section A very difficult. Any help with these questions would be much apprietiated. Homework Equations The Attempt at a Solution
  30. D

    A question related to Operational Amplifier.

    Hello. I believe there's a flaw in my understanding of the operational amplifier. I'm getting a bizarre result that I'd really appreciate if anyone can help me with. :) 1. http://tinyurl.com/6e9ovvp The part I'm having problem with is Q9 (b) (iv). 2. V=IR The Attempt at a...
  31. T

    Non Inverting Operational Amplifier

    Homework Statement Derive an expression for the gain Vout/Vin. Express your answer in the form of A+jB. Homework Equations The Attempt at a Solution If C is the capacitor in series with R1, gain = 1 + R2/[R1 + 1/(jwC)]. It says to express it in the form of A (real)+ jB (imaginary), but I'm...
  32. A

    Operational Amplifier: How Does It Work?

    Hi, I have a quick question regarding Operational Amplifier's. I understand in an ideal Op-Amp the current through the + and - input terminals should be zero. What is the point of the Op-Amp if no current goes through the inputs? How does it work? thanks
  33. L

    Assignment problem on Operational Amplifier

    The question is as given in the image attached entitled 'amplifier question' I would just like someone to check my working and verify whether it's correct or not. Thanks. And also want to ask on the second part which is 'what mathematical operation does this circuit perform?' Any help would be...
  34. T

    Why is an inverting summing amplifier used in audio mixers?

    why is an inverting amplifier and not a non-inverting amplifier used as a summing amplifier ? Why must the input voltages be inverted in a summing amplifier ? I am told that a summing amplifier is used as mixer in concerts where different music produced by different instruments go through...
  35. K

    Operational Amplifier Problem

    Homework Statement Given the attached figure (with values as shown on the op-amp) find Vo and io. Homework Equations None The Attempt at a Solution I figure that we're looking at an inverting operational amplifier and I used a voltage divider to find the input voltage...
  36. A

    Input and output of an operational amplifier

    Homework Statement The question is about the concept of the operational amplifier in electronics. For an ideal op. amp., it is said that the input impedance is infiinite and the current allowed by the op.amp. through its input terminal zero or in the case of a practical op.amp., it is...
  37. S

    Operational Amplifier Circuit

    Homework Statement Look up the offset current for the LM353 op-amp and predict the time rate of change of the output for the circuit below after the switch opens. (Find dVo/dt) Homework Equations offset current = 50 pA i+ = i-, ideally v+ = v-, ideallyThe Attempt at a Solution I really don't...
  38. T

    Operational Amplifier Dependencies

    Hi Does anyone know of any dependencies for op amps? for example: does it have a temperature dependence?
  39. V

    Engineering Integrator circuit using operational amplifier

    I read in a book that perfect integration using inverting op-amp is possible only when the time constant of the circuit(R1Cf) is lesser than the time period of the input signal. I have trouble in understanding this concept. Lets assume i give a square wave as input at the inverting terminal.Now...
  40. A

    Operational amplifier

    Hi I was just wondering what the nodal voltage Vb would be if you shorted the 1k resistor shown in this pic: http://img401.imageshack.us/my.php?image=opampem4.jpg also with that resistor in place what would the nodal voltage Vb be? i get 90.1mV ty in advance
  41. F

    Open loop gain of an operational amplifier

    Homework Statement How can the open loop voltage gain of an operational amplifier with AC input voltage be determined experimentally? Supply voltage for op amp is +9V. Homework Equations The Attempt at a Solution I'm really stuck here. I would appreciate some outline of...
  42. M

    Non-Inverting Operational Amplifier.

    Good evening. Right. My question is one of a simple nature, I think. Anyways, consider the following non-inverting Op-Amp design: http://www.freewebs.com/mushg/FWThumbnails/OpAmp.bmp Now, the basic formula for any non-inverting opamp is of course \frac{V_{O}}{V_{S}} = 1 +...
  43. M

    Non ideal Operational Amplifier problem

    hi... can anyone help with the problem i attached thanks in advance... I think a good start would be to convert the current source into a voltage source
  44. Amith2006

    Inverting Operational amplifier

    Homework Statement 1) Consider an inverting operational amplifier as shown in figure. Suppose R1= 1000 ohm & Rf = 10^6 ohm. It is said that the input impedance=R1=1000 ohm and the Output impedance= 0. 2) Consider a non inverting operational amplifier as shown in figure. Suppose R1= 3500...
  45. E

    Operational Amplifier with positive feedback problems

    Homework Statement I have some problems determining the tension output value for this circuit and this confusion comes from the presence of positive feedback and an alternate current.Since I'm used to negative feedback circuits and direct current it confuses me a bit,so any help is deeply...
  46. electronic engineer

    Operational Amplifier Course - Topics and Tutorials

    I want to inform you that our course about operational amplifier at university has such of the following topics: adder amplifier(inverting and non inverting)- integrator-diffrentiator-comparator- schmitt trigger-rectangular waveform generator-triangular waveform generator...and some active...
  47. S

    Operational Amplifier (Voltage Follower)

    Hi Guys, I'm trying to amplify a millivolt signal from an electrode that has a high input resistance (~ 200 MOhm). To avoid losses over the series resistance I'm using a high input impedance Op Amp TL071CP as a voltage follower. The problem I'm having though is that for some reason when the...
  48. N

    Sine oscillator with unipolar operational amplifier

    I'm trying to make a sine wave oscillator with unipolar amplifiers, and all the circuits I find are for bipolar amplifiers. I've tried to modify the bipolar circuit, but it doesn’t work. Can anybody give an idea or a circuit? thank you for your attention.