Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers,

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3answers
47 views

Understanding this comparator circuit for AC voltage protection

The circuit shown below is taken from this whole design. I understand the main idea. They want to measure some voltage condition and trigger something else with the comparator. R39 and C38 form a low ...
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1answer
44 views

Sampling Frequency and Bandwidth

If i have a Buck Regulator switching at 200KHz and i want to sample the Voltage and current using OpAmp in tha path connected to ADC(12 bit). What would be the sampling frequency to measure the ...
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1answer
36 views

Floating input in Op-amp Readout Circuit?

I was analyzing this circuit diagram in a thesis about a capacitive EEG electrode. The author talks about a flaw in the design where there is a "floating analogue input" that is causing the op-amp to ...
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1answer
97 views

What kind of amplifier design is this?

I am dissecting a design and I'm trying to wrap my head around the design pictured below. It is based on the TL064C amplifier and takes in single ended audio and outputs single ended audio as well. ...
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1answer
35 views

feedback loop component dc converter

Consider the schematics below, the switching frequency is 250KHz, So, The cross over frequency be 250/5 = 50KHz. My ADC is able to sample at 1MS/s which is good as from the SNR perspective.Now, the ...
2
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4answers
97 views

operational amplifier CMRR measurement

I am trying to measure CMRR of an op-amp and I found an application note from Analog Devices, that suggests the circuit below. I understand what CMRR means, but I can't understand why in the formula ...
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1answer
38 views

summing amplifier output

i amplified 2 audio signals using lm386 ics separately,and gave both the outputs as input to ua741 ic,to be used as a summing amplifier.I am not able to get any output at the speaker from ua741,not ...
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2answers
45 views

Amplifier Audio Ground to Signal Ground

I am using a VS1053 (on a SparkFun Music Maker shield) to provide audio for my project. I am taking a line out signal and inputting it into an op amp for signal processing, ultimately being input to ...
6
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2answers
2k views

Crowbar circuit causes unexpected behavior for op amp circuit

I am using an op amp to amplify an input signal from a microcontroller, which in general is working fine. For over voltage protection, I added the crowbar circuit taken directly from figure 32, page ...
1
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2answers
30 views

Can I use piezo plate instead of electret mic?

I am doing a project by following the steps mentioned here. It provides me the following circuit: Now, in place of the electret mic can I use a piezo plate? I need to use the same IC, i.e. LM358. ...
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0answers
25 views

Multisim opamp output oscillates for DC volt if it reaches saturation

Am trying to learn op-amps using Multisim. In the simulation I set initial condition to zero and set the circuit so the output reaches saturation point but instead its ringing with frequency 374HZ. I ...
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6answers
2k views

Why does this potentiometer in an op-amp feedback path cause noise when adjusted?

I have placed a dual-gang 100k potentiometer in the feedback path of two op-amps that work as a Sallen-Key filters. This controls gain but also the Q factor of the filter (somewhat demonstrated on ...
2
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1answer
83 views

What's wrong with this circuit built on opamps?

I have built this circuit in the LTSpice, but it refuses to simulate the operation using normal solver, but shows great results using alternate. This source says Be suspicious of circuits that need ...
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0answers
37 views

calculate the ouptut of two operational amplifiers in a series

i want to calculate Vs which is the output of this circuit simulate this circuit – Schematic created using CircuitLab so i just want to equation that can help me find Vs. please help me, ...
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1answer
43 views

Abuse TS339 comparator channel as a voltage multiplier

I have multiple free channels of a TS339 amplifier remaining and would like to use one of them to multiply voltages like this: simulate this circuit – Schematic created using CircuitLab Now it'...
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2answers
59 views

Op Amp integrator (square to triangle) not always start working correctly

I created an Op Amp integrator with LM358 to convert square wave to triangle wave as shown below. simulate this circuit – Schematic created using CircuitLab Though the circuit sometimes works ...
1
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2answers
82 views

Help With Buffer Amplifier/Filter Type Circuit

I’m having trouble with a circuit I designed and I would be greatly appreciative if I can get some help here. The circuit I designed is a buffer amplifier type design intended to take two channels of ...
-1
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0answers
34 views

How to drive lcd display?

I'm trying to figure out the basics of LCD screens in practice. I found a good video which tells it needs negative and positive voltage https://youtu.be/ZP0KxZl5N2o?t=767 I want to drive just one ...
2
votes
1answer
103 views

Can I use a JFET like this?

I'm trying to bias the inputs of an op amp, I can't simply use a resistor because there is a tiny cap at the input and it forms a voltage divider and I get no signal through. Can I use a JFET like ...
0
votes
1answer
87 views

High side current sensing

I want to sense 30 amps of current using op amp in high side. I know that there are many dedicated current sensing amplifiers for this purpose. But I'd like to try it with an op amp. I have tried high ...
-3
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1answer
68 views

I just purchased a batch of TL081CP opamps and would like to know what the codes on the bottom mean [closed]

There is a random marking on each one. none the same. What does this mean? e.g. 03, 1h31 In my batch, none are the same with leads me to think they would not be bach codes.
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1answer
24 views

Gain with inversing Op Amp on Equalizer

I know I posted a question about this circuit before, but I'm running into a problem. I know this is a terrible equalizer design but I'm trying to learn to put in use what I learnt with Op Amps and ...
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0answers
51 views

Designing a 4053 IC robotic control circuit for interfacing with Sabertooth motor controller?

I am designing a control circuit for a robot and was recommended to use a 4053 IC to achieve analogue multiplexing. PROBLEM The Sabertooth 2x60 motor controller I am using is running in analog ...
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3answers
90 views

Opamp input offset voltage…common mode?

Looking at the datasheet for an OPA197 opamp, I see this: What is the circled expression trying to tell me? The common mode voltage is equal to the voltage at the non-inverting input minus 1.5 V ...
5
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3answers
857 views

Non-inverting amplifier ; Single supply ; Bipolar input

I am working on the non-inverting amplifier using a single supply, which can amplify bipolar input signal. Non-inverting amplifier is working fine without any issues, only the negative portion of the ...
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2answers
33 views

LM2902 unity gain op amp, miss-wired

I am using LM2902 as a unity gain voltage follower to isolate measurements of a sensors voltage. ( datasheet: http://www.ti.com/lit/ds/symlink/lm2902.pdf ) the sensors i wan to measure operate at ...
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1answer
20 views

Inverting negative voltage back to positive with LM324

To be able to measure the value with an Arduino Nano I want to convert the negative rail voltage to positive. I tried to build a simple inverting amplifier with unity gain using LM324. The supply is +/...
4
votes
3answers
103 views

JFET stabilised wien bridge component ratios

I find myself in need of a sine wave oscillator and have decided on the wien bridge. I have followed all the tutorials but have a few questions that do not seem to be answered elsewhere. Firstly, I ...
0
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3answers
88 views

Op-amp input impedance

I was reading the following tutorial from Analog Devices: https://www.analog.com/media/en/training-seminars/tutorials/MT-040.pdf They include the following image and state: In most op amp ...
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2answers
87 views

How do parallel resistors and capacitors reduces frequency peaking in opamps?

I'm trying to understand a schematic from the front end of an analog discovery scope. It uses an AD8066 opamp, and has a resistor and capacitor in parallel on the inverting and non-inverting terminals....
4
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2answers
50 views

Low Level Photodetector opamp LTC1150

I found below schematic from LTC1150 datasheet (PG11) I want know what is the purpose of 10R resistor to ground. when I add this resistor to my circuit it reduce the noise (or peaks).how? After ...
1
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1answer
89 views

LTSpice simulate log amplifier

Consider we have a nonlinear opamp circuit like this. According to theory this op amp should take log of input. I wonder whether it is possible to get a response like this : I tried to plot vOut ...
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1answer
59 views

Why is my amplified strain gauge output so unstable?

I've attached a strain gauge to a bending arm of a robot, and it varies by about 1.5 ohms from 356 to 357.5 ohms. I place this in a whetstone bridge. The strain gauge is R3. R1, R2, and R4 are all ...
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2answers
74 views

Operational amplifier output voltage calculation

This problem asks for \$ v_O \$ in terms of circuit problems. I solved the problem. But my solution has \$ \large v_O = -R_4 (I_1 + \frac {V_1}{R_2} + \frac {V_2}{R_3}) \$ \$ I_1 \$ term as you'd ...
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0answers
60 views

Find the transfer function of an opamp circuit

I've the following circuit: simulate this circuit – Schematic created using CircuitLab I need to find the transfer function of this circuit. I did the following: $$V_+=\frac{R_1}{R_1+R_2}\...
1
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1answer
70 views

High voltage op amp rail generation

I'm using two ADHV4702-1 high voltage op amps for a project. They are configured as a current sink with a class B output amplifier (with some fixes for the crossover distortion). I already have a +/-...
1
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1answer
62 views

how to choose a dual power supply for rail to rail amplifier?

I need +15VDC and -15VDC dual supply for rail to rail supply of op-amp. I have found buck-boost inverters used for this task. I have a doubt whether the inductor in the buck-boost inverter circuit can ...
4
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2answers
93 views

DC on op-amp input, audio amplifier

I have built the following audio amplifier circuit on a breadboard. The circuit works. However the circuit makes a DC offset on the non-inverting input of the op-amp. simulate this circuit – ...
0
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1answer
64 views

Comparator Undesired Behavior

The following circuit is a comparator, which compares input square signal at non-inverting pin with fixed reference voltage at inverting pin of integrated comparator circuit LM393 (\$R\$ is collector ...
2
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2answers
50 views

Need help finding a high voltage, high slew rate Op-Amp [closed]

I am designing a single stage driver circuit that needs to be capable of driving a rectangular pulse wave up to voltages of +50V. The slew rate has to be at least 500 V/μs. So far, I have found 2 op ...
0
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1answer
50 views

Which Comparator could match this electronic circuit?

Below is a schematic of a current regulator using a comparator IC2. The board is from an XP-605 ELENCO bench top adjustable power supply. Searching the WEB was unsuccessful in finding any original ...
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1answer
36 views

Current source for high current LED driver- 24Vdc/max:16A

I am working on designing a current source for a LED driver, which can work up to max:16A, as long as stays On less than 500msec. Actually, the leds circutry is a Dome-light which is divided in 4 ...
0
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1answer
56 views

How to avoid the saturation of the current amplifier?

I have to calculate current gain of the following circuit and to model it in Spice. I arbitrarily set Is = 0.0002 A: Here are the results provided by LTSpice: Also, in order to find an equation for ...
0
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1answer
87 views

Noisy op amp buffer

I made an op amp buffer using a TL071 for my guitar but it is very noisy. The circuit is a simple follower. Originally I had no feedback resistor but I added it later in case it decreased the noise ...
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0answers
52 views

Derivative amplifier

I want to handle 8 and more buttons or switches with only a few MCU pins and receive interrupt whenever some of the buttons is pressed (even if some switches are active). I'd like to use PISO shift ...
0
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2answers
68 views

What's the voltage transfer characteristic of this power driver circuit?

[Exam problem for an instrumentation course] Can anyone help me understand how this circuit works? I'm not too familiar with power circuits... This somewhat reminds of a BJT class B amplifier (but ...
0
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1answer
40 views

How to select resistance to cancel offset output voltage due to bias current?

Consider the figure above how Rcomp was choosen. I know for simpler circuits like inverting amplifier and ideal integrator how Rcomp was calculated but following same procedure (that's using ...
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3answers
89 views

How to find input impedance of this OPAMP circuit?

Assume OPAMP to be ideal with infinite gain (a) and infinite input impedance I am clearly able to see that the input impedance of this circuit is R1 (correct me if I am wrong) but I am unable too ...
0
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1answer
64 views

Test cases for for OTA in LTSpice

Here is a component OTA provided by LTSpice which has inverting non inverting common and output node. I am in process of modelling this OTA behavior form LTSpice to PSpice. I reffered this link for ...
0
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1answer
42 views

Wheatstone bridge and difference op-amp

I use Wheatstone bridge as a dual voltage divider to feed both inverting and non-inverting inputs of differential op-amp: Theoretically voltage can be calculated using voltage divider expression: Va =...