Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers, which are DC-coupled high-gain electronic voltage amplifiers with a differential input and, usually, a single-ended output.

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How to measure voltage with a floating supply?

In the example below, ground of a dual supply is referenced to +Vout. Assuming we have a MCU connected to VCC and +Vout, if we then try to measure the voltage at +Vout with the ADC, we're basically ...
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5 votes
5 answers
379 views

Why does this op amp input stage have single ended output?

Looking at the internal diagram of LM324: I see that the output of the the input stage, which is a differential pair, is single ended rather than being a differential output. How does then this input ...
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0 votes
2 answers
130 views

Offset amplifier's input to prevent opamp clipping

We can do this: With AC coupling and biasing op-amp input. Summing using buffered resistor Using sum and difference inherited in OpAmp and sum signal with desirably created virtual ground 1 is good ...
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7 votes
4 answers
423 views

Is my summary of parasitic oscillation in op-amps wrong?

We were discussing negative feedback in op-amps with my community college instructor. I tried to learn ahead about the concept of parasitic oscillations in feedback circuits. I wrote a summary of what ...
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-1 votes
3 answers
68 views

Do active filters count as amplifers?

Can we consider active filters to be amplifers? If we use the folowing active filter design, and adjust R1 and R2 correctly that the gain is set to 10 for example, does the output signal comes out ...
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0 votes
5 answers
185 views

How to decrease distortion and efficiency of this circuit?

How to achieve efficiency of more than 70% and decrease the distortion of the circuit to 0.1% in THD, without affecting my Vpp=30 with the circuit below with both in 1k and 6k frequency of Vs? Update ...
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1 vote
1 answer
58 views

Pressure Transducer, Reverse and Shift Output of a differential amplifier

I am making a custom hydraulic brake for my sim racing setup. The original brake uses a potentiometer which outputs 3.3V at no brake pressure and 0V at full brake pressure. My pressure transducer, ...
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  • 19
0 votes
2 answers
117 views

Amplifying a DC guitar signal with an op amp

I am looking to amplify a DC signal that will range from 0 to 400mV by at around 5-10X and read it with my DAQ. I currently have a TLV271 and a UA741CP that I tried to use in a non-inverting circuit. ...
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4 votes
1 answer
172 views

Generated sound

I got these schematics from an arcade game released in 1983. These two circuits are responsible for generating two different sounds even though they look very similar. First one (sounds like a whistle)...
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  • 205
0 votes
1 answer
54 views

DC voltage attenuation

I need to attenuate 0-5V to 0-1 mV. The output of simple voltage dividers (normal op amps or resistor divider) can't be distinguished from baseline noise (baseline noise is 10-20mV.) How can I ...
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  • 235
0 votes
0 answers
39 views

Are there any ways to increasing the gain and ICMRs to this opamp?

Here's the netlist of this CMOS opamp schematics. ...
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1 vote
1 answer
55 views

Substract Offset Voltages of Operational Amplifiers

In the circuit below the two LM324 Operational Amplifiers are from the same IC. The Offset Voltage of each OpAmp is specified to be up to 7 mV at 25 ºC. The Offset Voltage mismatch is not specified or ...
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1 vote
0 answers
38 views

Transmit changing shunt resistor voltage value using analog optocoupler

I would like to use the IL300 to transmit the voltage of a shunt-resistor. The voltage value of the shunt changes between 0 up to 1 volt in 1ms depending on the load. On the receiving side of the ...
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0 votes
1 answer
130 views

Designing a two stage push-pull class B audio amplifier

I am designing a two stage push-pull class B audio amplifier with s 2N4401 used as my pte-amplifier stage and TIP31C & TIP32C as my push-pull stage where my RL is a 10W speaker. I am trying to set ...
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1 vote
2 answers
179 views

Op-Amp complex impedance

I am having some trouble understanding the background of this question. I think they are saying that as you sweep the frequency of Vin, the impedance Zin seen will be different as you pass through the ...
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1 vote
1 answer
58 views

Can we use an integrator circuit as a Hilbert transformer?

I want to know about the hardware implementation of Hilbert transform. Can an integrator circuit be used to introduce a -90° phase shift to the input signal?
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3 votes
5 answers
368 views

Concatenating first-order high-pass filters

I have the following circuit, which is an active high-pass filter with the knee frequency \$ f_{-3 dB} = \frac{1}{2\pi RC} = \text{1 kHz}\$ I wanted to concatenate two of those systems in order to ...
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1 vote
1 answer
50 views

Feedback loop gain not as expected in a differential amplifier

I am trying to build an approximate opamp with a differential amplifier and add a feedback loop to get the approximate wanted gain. I used a differential amplifier with a current source and a current ...
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6 votes
3 answers
513 views

How to choose the RC values between a buffer and an ADC input?

In the OPA365 specification sheet there is this example circuit where they add a RC filter between a unity buffer and input of an ADC. My understanding of the purpose of this \$ 100 \,\Omega - 1\...
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  • 1,310
1 vote
1 answer
61 views

Reading OpAmp Open-Loop Gain vs Temperature Graph

From the OPA140 datasheet here: https://www.ti.com/lit/gpn/opa2140 How do you read this graph? Because on the Y-axis the units are all weird and the numbers are strangely negative. The open loop gain ...
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1 vote
2 answers
96 views

14-Volt 6-Amp Power Supply Stability

Design Requirements: The purpose is a linear DC power supply for 12-volt aircraft, marine, and amateur radio equipment power source 20 volts @ +/-10%. (output 85W = 6A*14.2V) Rser on V1 = 0.4 or ...
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  • 41
0 votes
1 answer
40 views

Designing a second order HPF with a high gain common-source

I have a High gain (A = 22k) Common-Source circuit, and I was wondering If I can make a second order HPF like this circuit: My circuit is just an NMOS with an input at the gate, output at the Drain, ...
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2 votes
1 answer
67 views

OpAmp filter drive capabilities

My application requires a high input impedance. Therefore I am using 2 x TLV313 OpAmps as unity-gain buffers for my ADS1296. They also provide an adequate common-mode output voltage (2.5 V) for my ADC....
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  • 45
1 vote
3 answers
803 views

Designing 2nd order Butterworth low pass filter [closed]

I designed a 2nd order Butterworth low-pass filter, but it did not work correctly. What is the mistake in this filter?
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0 votes
3 answers
72 views

Output level of LM311 comparator

I am simulating the circuit above in LT Spice, where a LM311 (a LT1011 is simulated, but should be largely equivalent) is used to transform a (noisy) sine wave signal into a square wave. Value of R5 ...
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  • 103
3 votes
5 answers
543 views

Calculate Opamp output

I found below circuit in one of our old designs and I am trying to figure out How to calculate the output gain. simulate this circuit – Schematic created using CircuitLab I think I found answer ...
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  • 479
0 votes
1 answer
60 views

Photodiode amplifier circuit for VBP104FAS sensor

I am trying to create a photodiode circuit for this sensor so that I can connect its output to a microcontroller. I am following the document: https://www.ti.com/lit/an/sboa220a/sboa220a.pdf for my ...
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1 vote
2 answers
214 views

Designing an audio amplifier with push-pull output stage

I'm working on a push-pull stage audio amplifier. I'd like your opinion on whether I'm on the right track with this, both theoretically and practically. In this circuit I'll be using the following ...
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2 votes
0 answers
49 views

sine appoximation circuit for 4 quadrants [closed]

Referring to my previous query Sine function approximation circuit. How does this work?. Can anybody suggest method to transform the circuit to work on all 4 quadrants?
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  • 73
0 votes
2 answers
96 views

Design review: Fully differential telescopic operational amplifier

I used Behzad Razavi's book to design a fully differential telescopic op-amp [screenshot attached]. Then I follow the same steps to design my proposed opamp, but I am not getting the desired result. ...
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0 votes
2 answers
67 views

Calculating offset voltage [closed]

This is a circuit that is in my textbook, the derivation for the offset voltage is not provided only the end result is. I would really appreciate it if someone could please help explain how this is ...
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  • 11
2 votes
0 answers
74 views

MOSFET - Frequency response

I tried to do an exercise from my textbook where I have to discover the gain for mid frequencies of the MOSFET below, but I can't solve it. I got stuck at one point. I drew the small signal ...
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0 votes
2 answers
87 views

When I do a simulation in LTspice I receive errors

When I run the simulation I receive errors. I am a beginner in Ltspice and I do not know how to solve this problem. I have to draw from 1 to 6
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4 votes
3 answers
985 views

Why does does the power supply in my op-amp circuit need to be connected to ground?

In another question a user posted the following circuit. simulate this circuit – Schematic created using CircuitLab It was explained to the user that the op-amps negative supply rail should be ...
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5 votes
4 answers
355 views

Slew rate of two stage OTA

I have learnt two stage opamp designing from books and yourtube videos, but have always failed to understand slew rate formula which is I5/Cc(I5 is bias current of M5 and Cc is compensation capacitor)....
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-4 votes
3 answers
150 views

Cannot amplify DC voltage using op-amps

I am trying to amplify a DC voltage scaled from 5-10V to another DC voltage with maximum 12V. Why I am not using just a DC voltage with that value? Because the input DC is variable according to some ...
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  • 15
0 votes
2 answers
66 views

AD8065 Offset problem

I'm an electronic engineering undergrad and your discussions helped me a lot. As a project, i was instructed to design the front end for a data acquisition system. The specs as below. Supply +/- 5V ...
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1 vote
2 answers
56 views

Why doesn't my difference amplifier get saturated in LTSpice?

I'm currently simulating my high- side current sense amplifier for measuring mains current(along with the LP filter) .I also have the voltage sensing in the corner and I have attempted to simulate a ...
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-1 votes
3 answers
134 views

How to amplify DC voltage using Op-Amp?

In some real-application, a certain module is used, and the output voltage from this module is from 5 to 10 v. The required voltage should be scaled to 10, i.e. the 10v yields a 12v, 5v yields a 6v, ...
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  • 15
1 vote
1 answer
98 views

Why the LM358 working in this case and what the definition of "ground"

I asked this question previously Why this ZCD not working? and today I saw my friend using this AC voltage sensor module https://mikroelectron.com/Product/ZMPT101B-Single-Phase-AC-Voltage-Sensor-...
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  • 597
1 vote
2 answers
134 views

Howland current source for negative currents

I am currently in the process of utilizing the design of Howland in order to derive a source that is able to provide an \$I_{out}\$ between \$0A\$ and \$30A\$ at the output load \$R_L\$. As you can ...
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  • 27
0 votes
3 answers
121 views

Amplifying signal with op-amp 741 doesn't work

I have a 500 Hz sine wave with amplitude 1V, and I need to amplify this signal 3 times, i.e. the required amplitude is 3V. I tried to connect the circuit two times as shown below, using gain 3/1, ...
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  • 15
0 votes
1 answer
73 views

Op Amp diminishing rather than amplifying, but only inside the cutoff frequency of the filter it follows

I have a 7 stage passive Chebyshev filter designed to attenuate signals outside of a ~1MHz bandwidth centered around 50MHz in order to protect a clock input from frequencies that are too high or low. ...
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  • 51
2 votes
5 answers
540 views

High precision resistance meter

I'm designing a high precision resistance meter, which will measure the change of resistance of a given remote resistor, which is not placed on the circuit PCB, against temperature. I want to do this ...
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  • 995
0 votes
2 answers
96 views

Why this ZCD not working?

I have a simple drawing of ZCD by using potential divider to stepdown the voltage feeding to the inverting and non-inverting input of LM358N. The simulation result as below In practical, I connect ...
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  • 597
0 votes
3 answers
75 views

Ambient light sensor to a microcontroller

I am looking to make a small sensor board for something at home. I am familiar with embedded systems but my electronics knowledge may not be the best. For my situation, I would like to connect a ...
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0 votes
1 answer
68 views

Why can't we use crystal oscillators in series mode itself instead of parallel mode

I'm reading about the crystals and found that the crystal can be operated in series mode resonance as well as parallel mode resonance. In the case of series mode resonance, no external load capacitors ...
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  • 2,706
1 vote
1 answer
96 views

Problem on biasing of the differential folded cascode with ideal and non-ideal CMFB

For this circuit, a PMOS input stage folded cascode amplifier as a gain booster, I have two questions. The PMOSs (Mppp1 to Mppp4) in the cascode banches are in strong-inversion saturation while the ...
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  • 93
3 votes
3 answers
531 views

When do we add a resistor between the inverting and non-inverting terminal of an op-amp

simulate this circuit – Schematic created using CircuitLab In the above image, let's assume for namesake that the op-amp is powered and there are inputs at both the terminals. My question is , ...
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  • 2,706
2 votes
1 answer
110 views

Schmitt trigger Upper and Lower Threshold voltages

I speak with reference to this (Electrical4u - blog tutorial) and this (All about electronics - video tutorial) on the Schmitt trigger. From what I have understood, in the non-inverting schmitt ...
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