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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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Programmable gain amp vs op-amp + digipot

I'm currently developing a system where I need a signal amplifier with variable gain. I'm browsing the market for viable chips, and it looks like I have two options: Programmable gain amplifier ...
DELTA12's user avatar
  • 868
4 votes
3 answers
528 views

How to determine the signs of the op-amps in this circuit?

I have tried assuming OPA1 has negative feedback and then find the sign of OPA2 making assumptions on the latter. But the answer turns out to be wrong. How should I proceed with this question?
cheems's user avatar
  • 63
2 votes
2 answers
145 views

How to derive the average current drawn by the op amp in the given circuit?

For the circuit, I have calculated the output current to be (pi/20)*cos(wt) and the average of this is 0. But, since the initial conditions tell Ip= Im= 3mA, I thought the average current will turn ...
cheems's user avatar
  • 63
1 vote
2 answers
184 views

Where does my op-amp system of equations fall apart?

I was working on this problem: Find values for \$\{R_2, R_3, R_4\}\$ Assume ideal op-amp Gain of 100 Input resistance of \$1M \Omega\$ No resistor is larger than \$1M \Omega\$ And I build the ...
Freddy Mcloughlan's user avatar
1 vote
2 answers
173 views

Transimpedance amplifier with OPA838 - oscillation - supply voltage

This post is the continuation of my previous post: Transimpedance amplifier with OPA838 - instability Considering there were a lot of discussion, so we made this new post, to add for details, such as ...
Andromeda's user avatar
  • 473
1 vote
1 answer
78 views

Understanding this constant power laser driver circuit

I am trying to reverse engineer a constant power laser driver. Unlike constant current drivers, these use an integrated photodiode which monitors the laser diode output. The photodiode current feeds ...
selene flemming's user avatar
2 votes
2 answers
157 views

Best Practices for Preventing Oscillations When Interfacing an ADC with an OPA Output

I'm working on interfacing an ADC with the output of an operational amplifier. To mitigate signal integrity issues, my usual approach includes placing a small resistor near the OPA output and a small ...
nowox's user avatar
  • 847
3 votes
2 answers
426 views

How to share a single gain resistor among multiple op-amps in a circuit

I'm currently designing a circuit where I need to implement multiple op-amps, each configured with the same variable gain resistor using a single digital potentiometer. To simplify the design and ...
Bored's user avatar
  • 33
0 votes
1 answer
106 views

Op-amp with significant noise

I have the circuit below on breadboard. (Photodiode connected to op-amp in Transimpedance configuration) With LF351N (placed on the breadboard) as op-amp I'm getting nice signal on oscilloscope ...
LifeIsBeatiful's user avatar
2 votes
4 answers
553 views

Why doesn't my OP Amp comparator work in LTSpice? (AD8665)

When V2 > V1, Vout should output approx. 5.3V. When V2 < V1, Vout should be approx. 0V. But this op amp seems to always output 5.3V regardless what V2 is. What could be going on here? Is this ...
BobaJFET's user avatar
  • 1,012
3 votes
2 answers
274 views

Open loop gain of Op Amp 20 dB lower

I need some clarification regarding the open loop gain of Op Amp. I tried simulating this active BPF on LTspice. The Avol of the Op Amp U6 (UniversalOpamp) is 1meg and its GBW is 10meg. My ...
Res999's user avatar
  • 31
0 votes
1 answer
41 views

Frequency Companding

I have a theory question. I want to know if compressing and expanding audio frequencies is possible or perhaps already accomplished. As a point of reference, audio companding is a signal processing ...
Dereck's user avatar
  • 652
2 votes
3 answers
213 views

Buffered power supply with op amps?

I dont quite understand how this circuit works. I tried to simulate it on multisim 14 and got even more confused! Can anyone help me analize this circuit? I only understand the second stage (the ...
adgp97's user avatar
  • 21
4 votes
4 answers
2k views

Why does my integrator slowly saturate to negative rail in the following configuration?

So I have the following basic integrator circuit: The input signal is a 100mVp-p square wave of 50k frequency. In this case I get a stable triangle wave output. However, when I make the amplitude ...
needbrainscratched's user avatar
2 votes
1 answer
173 views

Simple example of first order ODE and Operational Amplifier

Hayt's (8th edition) Engineering Curcuit Analysis (Chapter 9, p360) contains an illustration of Operational Amplifier solving \$\frac{d^2v}{dt^2} = -9v\$. It is hard for me to understand how it was ...
user1700890's user avatar
0 votes
2 answers
152 views

Generate a fast, high amplitude pulse for measuring slew rate

I need to create a test set-up that measures slew rate of a few op-amps. The fastest slew rate among all of the op-amps in my list, belongs to NE5532 with 9 V/us slew rate and output amplitude of ±10 ...
Fateme's user avatar
  • 338
1 vote
1 answer
61 views

Time period of V1 and V2 signal the integrator and schmitt trigger

Hello I have tried to solve this circuit several times and i cant figure out what i did wrong. You guys give me some tips. This is circuit with 2 op amp (2 stages) first one is schmitt trigger and the ...
miguel747's user avatar
0 votes
0 answers
55 views

Is it necessary to match the operating ranges of the two stages in a two-stage amplifier

I'm trying to design a two-stage amplifier as shown below. What confuses me is that - is it necessary to match the operating range of the two stages (ie. Vocm of the first stage is within the Vicm ...
Jack Black's user avatar
0 votes
1 answer
103 views

What is the quiescent current in a current limiting voltage regulator circuit?

Is the quiescent current simply the current drawn by Q1 and Rin when no load is connected to the output? How would this differ from the supply current?
user998479's user avatar
6 votes
4 answers
980 views

Implementing guard trace/ring in PCB design for opamp having high impedance input

In the circuit below I am trying to create a "guard ring" for the opamp with high input impedance (~1T Ohm) to avoid femtoampere current leakage. I'd like to ask you guys if I did it right. ...
Phạm Sáng's user avatar
1 vote
3 answers
120 views

Calculate the transfer function of an OPAMP circuit [closed]

I have an OPAMP circuit that its output increase steadily without cahnge in the input. I guess the issue is in the transfer function of the circuit and its stability. I want to calculate the transfer ...
MMB1999's user avatar
  • 19
-1 votes
2 answers
95 views

Building a unity-gain op amp with speaker?

I am trying to build a voltage follower op-amp circuit to hear a sine wave but I can't get it to work. I was using the LM386 but then found out that it has a gain of 20 by default so I can't use it. I ...
Electrolyte's user avatar
2 votes
2 answers
129 views

Excessive DC offset in high-speed opamp amplifier circuit

Background A while ago I got my dad's old Musical Fidelity A1 MKI integrated amplifier from the early 80s (I believe). I found a blog that featured a lot of interesting information about this ...
jonatan.wilund's user avatar
0 votes
2 answers
98 views

How to measure fully differential amplifier input impedance in PSpice?

Before the differential ADC, I have a fully differential amplifier as the front end. I want to simulate and measure differential input impedance. My working range is max. 20 kHz. Why am I using the ...
Electronx's user avatar
  • 756
1 vote
2 answers
82 views

Using an LT1357CN8 to amplify the signal of a 1.5 MHz frequency generator

I am working on a frequency generator to control piezoelectric transducers. I use an Arduino Uno R4 Minima to send data to an AD9833 which creates my desired sine wave up to the required 1.5 MHz. ...
ForzenikHD's user avatar
0 votes
1 answer
57 views

Ground Fault Interrupter

I was trying to simulate a circuit where it can detect grounded neutral conditions in the household. I need to have a current transformer which can detect the current differential ans sends a signal ...
M S's user avatar
  • 1
5 votes
2 answers
752 views

Slew rate and Bandwidth for 5 MHz signal

I'm trying to amplify a sine wave signal with opamps of high bandwidth and slew rate. It works fine up to about 700 kHz, then the gain decreases and about 1 MHz it's only 1, when it should be about 5. ...
Gos's user avatar
  • 589
0 votes
1 answer
62 views

Ideal headphones impedance/sensitivity for op-amp

The maximum output voltage of my audio source is 3 Vpp and the maximum output current of my amplifier (op-amp AD4075-2) is supposed to be 45 mA. What would be the ideal impedance and sensitivity of ...
Domingo's user avatar
  • 109
0 votes
1 answer
81 views

Will voltage at the inputs/outputs destroy an unpowered opamp?

I have a circuit powered by 12V that accepts an input signal of 0V to 10V. The circuit shall act as a buffer to the signal, with an added LED indicator. In certain circumstances, the circuit itself ...
one_three_three_seven's user avatar
0 votes
2 answers
86 views

Using a square and/or sine wave generator through a speaker [closed]

I have recently undergone some university study which introduced square and sine wave generators, I was wondering if there's a specific speaker I could use (its inputs would be a power supply and the ...
sage_lessthan_3's user avatar
0 votes
1 answer
62 views

Options for line output doubling as headphone output

As the title says, I'd like a combined line/headphone audio output with the following design criteria: ideally driven from 5V single supply (12V available, but noisy) flat frequency response, also in ...
one_three_three_seven's user avatar
0 votes
1 answer
55 views

Stability of a constant current sink( opamp+nmos)

I am using opamp and a mosfet as constant current source. My current is from 0mA to 25mA. Opamp-TLV9002 (GBW-1Mhz at 5v , phase margin - 78deg at 5.5v and gain as 1 ) Mosfet- nmos- Bss123lt1g ( input ...
funtastic rdj's user avatar
3 votes
2 answers
228 views

Exercise of expressions for ideal op-amp based amplifier circuit

(i) Obtain an expression for the CMRR of a difference amplifier, in terms of the tolerance of the resistances used in the amplifier. Hint: Assume that 𝑅1/𝑅2=(𝑅3/𝑅4)(1+𝛼), where 𝛼 is the degree ...
G Shri Meenakshi's user avatar
0 votes
2 answers
90 views

uA741 OpAmp output current never approaches "TYP" output short circuit current

I am trying to use a uA741 Op-Amp (I cannot use a different Op-Amp) to build an amplified half wave rectifier circuit. I was able to successfully build the circuit, however the zener diode that I used ...
Samantha Garcia's user avatar
-1 votes
3 answers
54 views

Virtual short condition contradicts the equation for an op amp output voltage [duplicate]

I'm trying to understand how to analyze basic op amp circuits. From what I have found, the output voltage of an op amp is equal to the following equation: ...
universitystudenttryignhard's user avatar
1 vote
2 answers
97 views

Op-Amp Selection for Dummies

I am new to op amps, and I could use some help. I am trying to make a linear precision current supply and searching for the perfect op amp for the job. I have a design I know that works, at least on ...
Dereck's user avatar
  • 652
0 votes
1 answer
58 views

OpAmp Input Impedance vs Load resistance

I have below photodiode that provide low rise time based on 50 ohm load resistor. However I'm planning to use it with opamp in transimpedance configuration. In this configuration, current is running ...
LifeIsBeatiful's user avatar
11 votes
4 answers
1k views

Why is the level wiper wired like this in the op-amp stage?

I have come across a mixer that I am going to rebuild, and maybe try to replace the volume potentiometers with a digital variant. The picture shows part of the schematics (after 3-band EQ, and before ...
DennisHolm's user avatar
1 vote
1 answer
148 views

Op-amp with two series capacitors

Consider the circuit below. Let \$V_i\$ be switched on at t = 0. We want to find an expression that related the output voltage \$V_o\$ to the input \$V_i\$, in terms of R1, R2, C1, C2. Here is my ...
student1's user avatar
  • 767
3 votes
1 answer
57 views

Using Laplace transform to solve integrator circuit

I need to find Vout in time domain for below circuit. Here's my attempt, using Laplace transform. $$V_{in}(t) = V_0 \sin(\omega t)$$ From the above equation, Vin in s-domain is then: $$V_{in}(s)=V_0\...
user97662's user avatar
  • 283
3 votes
4 answers
201 views

How can I find Thévenin equivalent circuit of the NFB op-amp input? [closed]

I need to find the Thévenin equivalent of the right side of the circuit by looking into node E and F. How can I find it?
LSK's user avatar
  • 41
0 votes
0 answers
58 views

capacitive soil moisture sensor connected to attiny85

je suis en cours de créer une circuit électronique d'un capteur d'humidité du sol capacitif avec un aop pour amplifier le signal sortie de capteur , et ce capteur relie avec le microcontrolleur ...
Ayda Benayed's user avatar
0 votes
2 answers
95 views

Is my equivalent op-amp for this circuit correct?

The following is a question from 8.18 in Design of Analog CMOS Integrated Circuit, page 342. Consider the circuit in this following figure. \$(\frac{W} {L})_{1-4} =\frac{50} {0.5} \$, \$|{I_D}_{1-4}| ...
kile's user avatar
  • 897
1 vote
3 answers
104 views

Why is my band-pass filter self-oscillating?

I built a bi-quad filter based on the AD8054 (consist of four AD8051 op amps) following exactly the AD8051/8054 datasheet. After I power up my op-amp, the filter entered a steady self-oscillating even ...
BenjaminZ's user avatar
3 votes
3 answers
582 views

Proving formula for feedback for operational amplifiers

Positive and negative feedback circuits : let the following circuit I want to prove that this system is stable (meaning the op-amp isnt getting saturated) if and only if \$ k_+ = \frac{R_{1+}}{R_{1+}+...
Knowledge Seeker's user avatar
1 vote
4 answers
95 views

LTspice: triangle wave circuit not producing any waveform

I've implemented this circuit in LTspice from this Triangle Wave Generator tutorial. Unfortunately, when I run the simulation, it doesn't produce a wave at all, just a flat VDC output. Any help would ...
Abstract's user avatar
  • 111
0 votes
0 answers
67 views

OpAmp on Multisim keep amplifying over Gain Bandwidth Product

I have below circuit on Multisim with Current source replicating Photodiode and opAmp amplify current. However opAmp keep amplifying even at very high frequencies without considering Gain Bandwidth ...
LifeIsBeatiful's user avatar
1 vote
1 answer
78 views

LTspice - simulation of SPWM is giving unexpected result

I am trying to make SPWM with op-amps. I also made a simple NOT gate with a simple transistor. The first op-amp is working well when its output is not connected. When I directly connect the first op-...
Mhan's user avatar
  • 355
4 votes
4 answers
644 views

How to prevent this op-amp from railing

I have the following circuit: An input that can go negative (+/-5 V sine wave), and two inverting op-amps. The second op-amp is "current buffered" and is driving the base of a BJT. Here is ...
DarkBulle's user avatar
  • 395
3 votes
1 answer
180 views

Why use of asymmetric power supply in Op Amps for this audio device?

I am learning about op amps and audio devices, and decided to run a simulation of the following device: https://www.electrosmash.com/klon-centaur-analysis I started humble, and run the simulation in ...
Facu's user avatar
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