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Questions tagged [op-amp]

An op-amp (operational amplifier) is a high gain analog voltage amplifier with differential high impedance inputs, and a low impedance output. A basic building block in signal processing, like as amplifier or active filter.

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How does one do nodal analysis on this circuit?

I am having troubles trying to figured out the analysis of this circuit. simulate this circuit – Schematic created using CircuitLab Here's my attempt on trying to do nodal analysis on the ...
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61 views

Stability of op-amps: “Oscillations if phase = 180° and loop gain > 1” question

I'm trying to understand the stability against oscillations for op-amps in a feedback circuit. A common argument I've seen on many sites goes as follows: The closed-loop gain is given as $$A_{\text{...
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61 views

Basic Ideal Op Amp Circuit Analysis

I am trying to familiarize myself with operational amplifiers by going through this book by Sergio Franco. This is a basic question regarding the example given on page 16, which I am struggling to ...
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37 views

Active Integrator Parallel Capacitor in Feedback

I am designing an integrator circuit, looking to perform in the range of 10-10kHz - and I had a thought and I cant find any information online about it. For low frequencies of 10Hz, the reactance of ...
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79 views

Need help explaining behaviour of a circuit

just can't wrap my head around this one for some reason. I am sorry if it's easy for you to see. Just confused on the duality of things in circuits, Is it a filter? Or is it a peak detector? How do ...
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42 views

Precision Rectifier confusion

Its been a while I took a long hiatus due to not having a scope any longer, but I finally saved up and got myself one. I was playing around with a precision rectifier (OPA350PA) and I came across ...
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51 views

measuring output impedance of op-amp

I've just took for granted the fact that the input impedance of op-amp is high and output impedance is low. I was reading "the art of electronics" lab book and there is an exercise that asks you to ...
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61 views

Is there current flowing out of an Operational Amplifier output?

I came across the following self-study problem, taken from The Analysis and Design of Linear Circuits (8th edition). I was not intending to solve the problem, since I am just looking over all ...
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91 views

Reasons for choosing a transistor instead of an op-amp as a buffer

I have often seen circuits for guitar pedals that use an emitter-follower configuration as the input and output buffer (see example below). If an op-amp can provide a greater input impedance / lower ...
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Overshoot/undershoot issues in load current wave form of a MOSFET

We have designed hardware circuit which validates voltage regulator maximum output current. So we designed op-amp circuitry to control gate drive of the Power MOSFET and it will work in active region ...
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32 views

OPA Noise Calculation

This question is somewhat general but I will ask in terms of an example. Following is the general noise calculation for a noninverting negative feedback amplifier with the corresponding transfer ...
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103 views

Is there a difference between specialized audio amplifier and general op-amp silicon?

I've been doing some research into creating a DIY audio amplifier from line-level inputs to speaker level power. I found a guide centered around the LM386 Low Voltage Audio Power Amplifier on YouTube ...
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52 views

How does common mode range include the negative rail?

How do the devices like AD8220 handle the common mode voltage equal to the negative rail or even lower voltage (Take a look at figure 30 of AD8220 datasheet) ? Does the operation of the amplifier ...
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Can I replace electret microphone with audio connector and expect similar results (sound levels)?

Last night I built a circuit that allows me to obtain sound via a SEED Grove Sound Sensor and input it into my MKR Zero for frequency analysis. It's as simple as this: simulate this circuit – ...
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50 views

Resistor values for OpAmp circuit with dc offset applied to inverting pin

$$ \newcommand{\rth}{R_{TH}} \newcommand{\vth}{V_{TH}} \newcommand{\rf}{R_{F}} $$ Asked this in the math stack exchange, who recommended asking here instead. I'm stumped (hence posting here!) with ...
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42 views

Using an active bandpass on a very small signal

I am trying to design a active bandpass filter for an electret microphone (the output will then be read through a microcontroller to control some LEDs) (Image source - Electronics Tutorials) I want ...
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Design 230V rectifier i.e dc power supply [closed]

Please help me with this project as soon as possible.
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3answers
126 views

Inverting OpAmp with voltage divider in feedback loop

Last week I was looking for a programmable gain amplifier (PGA) with high gains (> 100V/V) and low noise. As far as I know most of the PGA integrated circuits out there are just (inverting) amplifier ...
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Op-amp Frequency Response [duplicate]

An op-amp is connected in the inverting configuration with Rfeedback = 20 kΩ, R1 = 33 kΩ. The frequency response of the closed loop amplifier is found to fall off at a frequency of 1.2Mhz What is the ...
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53 views

High resistance op amp

I'm making a simple op amp circuit to use it as a compactor. I connect the non-inverting point to a simple circuit and the inverting to a 3 volt dc supply. the circuit should compare the voltage at ...
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2answers
58 views

LM324 with arduino as a differentiator for phototransistor signal

I want to measure the rate of change of voltage with respect to time coming out of a phototransistor, and preferably amplify it at same time, as the change is not so significant. But lets just not ...
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49 views

How would I go about measuring an analog signal that has both positive and negative voltages on an arduino analog pin at a high sampling rate?

I have a signal that fluctuates between -70mV and 50mV. How would I get the arduino mega to read this on an analog pin at a high sampling rate? Ultimately I am trying to graph the data in real time so ...
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83 views

Is there any difference between AD620 vs INA128?

I'm trying to make an EMG sensor. I've found some tutorials, for example, DIY muscle sensor/EMG circuit for a microcontroller, but my main question is can I make an EMG sensor using AD620 instead of ...
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123 views

Constant current source with MOSFET, OPAMP and Instrument Amp

UPDATE Based on the information from everyone answering below, I have modified my circuit and the oscillation has completely vanished! I started performing small modifications in order of easiest to ...
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2answers
79 views

Why are my op-amp (LMC6484) output signals not independent of each other?

I am using a quad op-amp (LMC6484) in a non-inverting circuit. Using only one of the 4 op-amps I was able to amplify Vin = 80.3 mV to Vout =1470 mV. Rin=2.66k Rf=10k. V+= 9V… V- = -9V My problem is ...
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111 views

Current Regulation Drift

Consider this current regulation circuit, where a load is connected between a rail and D: R1 is 56k, C122/123 are 300pF, R201 47k and R200 680ohm The circuit works fine, but there is something that ...
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55 views

Help with design a mic preamp with opamps for PGA and ADC

I want to sample an audio source using an electret microphone and analyze the spectrum of it with a uC. I'm interested in the 100Hz-2.5kHz range, so I calculate with these values when I tried to ...
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4answers
114 views

Under what circumstances would the large internal input resistance of an actual op amp affect circuit operation?

I was able to find a lot about why the input resistance is high and basically infinite. I understand that the input resistance is high so that it doesn't become a load on the signal. I also know that ...
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Ideal Op Amp (Integrator and Differentiator)

I'm working on at a ideal op amp integrator and differentiator but i`m actually do it with the non-Ideal op amp but i have to do it with the ideal model i simulated in OrCAD/SPICE and i have a doubt ...
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2answers
755 views

How to estimate the analog bandwidth?

I have created the low cost oscilloscope and need to estimate the analog bandwidth. I do not have any specialized equipment and just trying to estimate it by watching the response to the square ...
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1answer
143 views

Why does the op amp output in this circuit have low slew rate?

I have the following circuit on a bread board (with the exception of using AD820 instead of AD822 - the main difference based on the datasheets seemed to be one versus two op amps in one package). ...
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1answer
56 views

Opamp confusion

I would really appreciate a little help here if someone explain me why his Voltage is 4v while mine is 10/3 and one more thing: whats the point of Applying KCL at node 1 when 5v is already known at ...
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49 views

Integrator (Op amp) Simulation OrCAD

I'm working on in a integrator op amp and actually i make the desing in a breadboard and is working but in time of simulation is like there is not voltage in the output of the op amp. I don't ...
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50 views

Voltage Amplifier using Op Amp 741 [duplicate]

I am trying to build an amplifier using op amp 741. But I am failing to build it on breadboard. I am connecting the positive end of a 9 V battery to pin 7 and negative end to pin 4. As per my ...
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1answer
80 views

Differentiator (Op amp) with a square wave

I'm working on a differentiator (op amp) with a unitary gain i calculated the value of RC and the period with a frequency of (1kHz). Figure 1. Differentiator Schematic (OrCAD). This is the schematic ...
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1answer
24 views

VFA vs. CFA Compensation Capacitor Comparation

Here, I am referring to voltage-feedback amplifier (VFA) and current-feedback amplifier (CFA). A basic schematic is given below for each. I.) VFA II.) CFA I am curious about the position of ...
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59 views

loop gain, open loop gain of op amp in inverting configuration (feedback capacitor)

I was trying to understand the 2nd answer from this post here, with the circuit of the post shown below. The 2nd answer has equations including open loop gain I wasn't able to understand (1st ...
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Adding voltage follower at the input of INA146

I planing to use an INA146 precision difference amplifier to do voltage level conversion from 0-12v to 0-3.3volt. Since the input device should be possible to change I like to add voltage follower on ...
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1answer
47 views

Problem encountered while amplifying load cell signal with LM358

I have an S-type load cell to measure weight up to 100 Kg. Its datasheet mentions 3mV/V against full range and excitation voltage. When no weight is applied, the voltage is 9.9 mV (Excitation is 10 V)...
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140 views

How does this opamp full-wave rectifier work?

I want to understand how the following circuit works. I understand OpAmps, diodes, and voltage dividers pretty well; but put this circuit together, and I don't know how it affects positive or negative ...
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34 views

Using a different op-amp model for the project

I have a project to complete and i have been told to use the MCP602 Operational Amplifier, but since that model is nowhere to be found where i am living, i wonder if i can use two LM741 op-amp instead?...
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1answer
52 views

Using Opamp as rectifier

Schematic below is a current sensing circuit, Rs is 35u sensing resistor and current I1 is bi-directional. I am confused on why diode D2 makes this circuit a full rectifier. Schematic: Simulation ...
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163 views

How can I determine whether this is a “rail to rail” opamp from its datasheet?

I know that rail to rail means that the opamp output can have a swing upto its power rail voltages. So for a rail to rail opamp lets say if the supply test condition is +-12V, I would assume that the ...
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1answer
39 views

OpAmp openloop threshold between inputs

I have read about OpAmps in openloop configuration where thy output +V,0,-V depending on the inputs. when the inputs are equal, the output should be 0. My question is, what can be the threshold or ...
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1answer
56 views

effect non- inverting resistor in the integrator op amp

While looking into integrator op-amp circuits, I came across two different implementation. In one the non-inverting terminal is grounded . While in the other there is a resistor in between. Can ...
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1answer
44 views

Need help choosing resistors for difference amplifier

In the circuit below I am trying to achieve 15.56 gain on IC2. The following combinations (in kOhms) are fairly close: 20/1.3 or 200/13 = 15.38 47/3 or 470/30 = 15.67 51/3.3 or 510/33 = 15.45 56/3.6 ...
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467 views

What circuit can be used to match input to output voltage by using an opamp?

What is the simple way matching an input voltage range to a desired output range. To be more specific with an example: If I want to convert/match 0V-5V input range to 7V-15V output range linearly, is ...
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1answer
58 views

What's this amplifier filter configuration?

I've come across an audio amplifier circuit that contains this following configuration: I recognize R1,C1, and R3 to be part of a first order high pass filter, but I'm not sure what C2 and R2 are for....
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1answer
55 views

Fluctuating Non-inverting opamp o/p

In the non-inverting amplifier shown below, when the DAC output (TP1) is held constant at 2.5V (same input code), the OP213 opamp output (TP2) fluctuates between 8.750 and 8.775V i.e., roughly 25mV. ...
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49 views

Measuring current vs voltage

Let's say that I have a periodic charge build-up across the capacitor C1. I could either choose to measure the current using a transimpedance amplifier as shown below or could measure the voltage ...