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.

Filter by
Sorted by
Tagged with
0 votes
0 answers
20 views

Differential pair with active load including resistance [closed]

In solving the differential pair with an active load, I am able to find the gain without including R1 as shown in the figure. When R1 is included, I am stuck on how to proceed. Could you help me out?
user avatar
2 votes
1 answer
42 views

DC offset of DC signal with op-amp

I have a DC signal from a DAC in the range of [0:3,3]V and want to convert it to be in the range [-5:5]V. My approach would be to scale with op-amp with gain 3 and then DC offset. I've read that this ...
user avatar
0 votes
2 answers
69 views

Op-amp voltage comparator

I am using an op-amp (LF353P) for my voltage comparator circuit. The supply voltage for the op-amp is +12 V and -12 V. The input voltage for the inverting pin (Vref) is 1.1 V. The input voltage for ...
user avatar
  • 13
4 votes
2 answers
82 views

Rescaling voltage input

Measuring laser transmission with photodetector, I obtain voltage values in the range of [0:9]V. The output of the photodetector is to be observed on oscilloscope and taken as input in ADC of Arduino ...
user avatar
3 votes
1 answer
73 views

Does op-amp virtual ground only apply in steady-state?

Does op-amp virtual ground principle only apply in steady-state? Assuming a negative feedback config of course.
user avatar
  • 2,575
0 votes
1 answer
42 views

Does op-amp virtual ground hold in open-loop config?

An op-amp is defined by the following equation $$ Vo = A(Vp - Vn) $$ Rearranging, $$ Vp-Vn = Vo/A $$ A real op-amp will have a gain around 100 and the output will be limited by the supply voltage say ...
user avatar
  • 2,575
0 votes
1 answer
18 views

Instrumentation Amplifier Simulation INA122P Output Voltage not zero (TINA-TI)

I have the following circuit, the INA122 instrumental amplifier. when RG pins are not connected, the default gain is 5. I am sure that the bridge is balanced, however, for the simulations, why there ...
user avatar
1 vote
1 answer
36 views

How to control high current voltage with small current voltage linearly?

I want to make an 18650 charger without a microcontroller for fun, I was designing a very simple circuit but I had a problem with adjusting the voltage if current/voltage excceds max current/voltage. ...
user avatar
  • 153
5 votes
4 answers
100 views

How to improve this precision rectifier by further decreasing cross-over transition times?

The Circuit The rectifier comes from TI's TIDU030: Precision Full-Wave Rectifier, Dual-Supply application note. My "benchmark" used as a baseline for evaluation is as shown below, powered ...
user avatar
5 votes
2 answers
231 views

How to add gain to this op-amp based precision full wave rectifier?

The design for the rectifier is rather clever, and comes from TI's TIDU030: Precision Full-Wave Rectifier, Dual-Supply. It looks as follows: simulate this circuit – Schematic created using ...
user avatar
2 votes
1 answer
39 views

OPA548 not generating correct output pulse

I have created a circuit for which I would like a rail to rail output of 0 - 15V, using an OPA548 with the driving waveform generated by a microcontroller DAC powered by 3.3V. The datasheet for OPA548 ...
user avatar
  • 108
3 votes
1 answer
70 views

Why is my oscillator way too different from simulation results?

How's going dear engineers. I hope your everything's going well. I've made a sawtooth waveform oscillator aim for about few hundread kHz. I didn't see any problems on simulation results, everything ...
user avatar
1 vote
1 answer
24 views

Measuring current of GUVV-C20SD diode with transimpedance amplifier

My goal is to measure the UV light using this UV diode and a trans-impedance amplifier, but I need help with the understanding of similar circuits. I have checked out the following image and I don’t ...
user avatar
  • 390
3 votes
2 answers
271 views

Op-amp integrator gain from calculation doesn't correspond with real-world measurement

In my integrator circuit, I added one feedback resistor R2 and one bias compensation resistor R3. The values of the components are values I have measured before I applied them on this PCB Evaluation ...
user avatar
  • 43
5 votes
1 answer
72 views

Instrumentation amplifier cross-connection circuit

I am trying to implement a circuit from an ADI app note that I have not seen anywhere else : Here it is in PDF format which is a copy of this article. I strongly encourage reading it as it is quite ...
user avatar
  • 133
0 votes
1 answer
70 views

Calculated crossover frequency of Op Amp integrator doesn't match the simulation

I am calculated the crossover frequency of my integrator circuit with the following formula. \$ f_{0\text{ dB}} = \frac{1}{2\pi R_1 C_1} \approx \underline{\underline{154\text{ Hz}}}\$ Unhappily, the ...
user avatar
  • 43
-1 votes
0 answers
44 views

Help designing a 3-phase inverter [closed]

I was tasked with designing a simple-ish 3-phase inverter circuit, but I am not quite sure where to start. My first thought was to phase shift the pulse from a 555 timer using something like this: ...
user avatar
6 votes
3 answers
431 views

Op-amp simulation

I am not sure what's the mistake I am making in the below simulation. Below is an MCP660 non-inverting op-amp with a gain of 3. Case1: Input: 1 MHz; Offset: 0.5 V; Pk-pk amplitude: 0.2 V Result: The ...
user avatar
  • 2,674
4 votes
2 answers
218 views

Possible causes of ceramic capacitor damage on high-voltage op-amp supply pin

I am working on a waveform generation board. The board contains +-200 V supplies and +-24 V supplies. The board takes a low voltage (+-15 V) waveform from a DAC on separate board and outputs +-200 V ...
user avatar
  • 69
8 votes
3 answers
645 views

Photodiode speed limitation

I have a system which demands optical data transmission since rotating parts are present. A mixed mechanical-electrical engineering project has led us to use photodiodes to receive data from one ...
user avatar
  • 1,126
0 votes
1 answer
50 views

Adding current follower in the circuit: error [closed]

I have the below circuit and when I add the current follower op-amp circuit it doesn't work. When I add an ideal op-amp it works, but when changing it to a realistic op-amp it doesn't. What could be ...
user avatar
2 votes
3 answers
161 views

Op-amp gain not working as expected

I'm trying to amplify a really small (1.3 mV) voltage from a sense resistor. I am using the following schematic: My load is an LED and resistor. For R2, I'm using a 470 kΩ resistor. For R1, I'm using ...
user avatar
  • 129
0 votes
1 answer
62 views

How did they consider \$I_{3_{min}}\$ and \$I_{3_{max}}\$ in 4-20 mA current transmitter? [closed]

Define the minimum and maximum currents through R3. See Design Note #5 before defining these currents. For this design, \$I_{3_{min}}\$ = 20 μA, \$I_{3_{max}}\$ = 100 μA are chosen. This link has the ...
user avatar
0 votes
3 answers
121 views

Simulating voltage divider?

Over the past weeks, I've been looking into an analog method of dividing 2 voltages such that V1/V2=Vout. I found many sources on Google using methods like log and antilog amplifiers or a multiplier, ...
user avatar
1 vote
0 answers
56 views

Why is Hf negative while Vf is positive? Aren't they the same but without Vin?

For the inverting op amp, I've seen the equation Vout/Vin = Hf/Hr Hr is the same as Vr but without Vout. Why isn't Hf the same as Vf but without Vin? What I mean is that Vr = Vout[R1/(R1+R2)] and Hr = ...
user avatar
0 votes
2 answers
45 views

Op-amp non-linear Bode plot

The figure below is an op- amp's Bode plot. In the ideal situation, there are no fp1 and fp2 in there. I would like to know why the real op-amp will have these two poles. Is there any document I can ...
user avatar
  • 475
0 votes
2 answers
81 views

How does feedback factor works in equation V-/Vout [duplicate]

I am asking this question to understand this. It states that V-/Vout is equal R1/(R1+R2) Here : V- is equal 0V. Because V+ is grounded. So V-/Vout = R1/(R1+R2) => V- = Vout*R1/(R1+R2). But V- is ...
user avatar
0 votes
1 answer
56 views

What is the feedback factor in the inverting Op Amp?

I've got a question about feedback factor. Because I don't know how to calculate it. I've been talking with some people and they say that feedback factor here is equal -R1/R2. Which is the reverse of ...
user avatar
1 vote
3 answers
98 views

Buck converter adjustable output-voltage using digital potentiometer [closed]

I am trying to design a buck converter using an LM2576HV (Vref: 1.23 V) and a digital potentiometer (input: 48 V, output: 0 to 48 V, Imax= 3 A). The digital potentiometer with the highest supply ...
user avatar
1 vote
1 answer
44 views

Asking experience for this flow-through pressure sensor: 26PCAFG6G - Honeywell

I have the following sensor:26PCAFG6G The output of the signal is a differential output from a Wheatstone bridge with 0 - 1 psi, or 0 - 70.3 cmH20 corresponding to 0 - 16.7 mV, I am using AD623AN for ...
user avatar
1 vote
1 answer
51 views

Does increasing gain of an op-amp improve transient response speed?

Consider a simple op-amp in a feedback configuration. You can consider the op-amp to be dominant pole compensated and approximated as a first order system. Let's say that the transient performance (...
user avatar
  • 2,575
0 votes
1 answer
34 views

Is a buffer stage needed in this signal chain?

I am designing a signal chain that includes a 4 pole cascade Sallen-Key filter based on the AD8034. The circuit will be used to shape tail pulses (~10ns rise time, ~50us decay) into gaussians. The ...
user avatar
  • 653
0 votes
0 answers
43 views

Operational amplifier controlled LED voltage (power supply)

I am trying to use two APEX PA12A to control two groups of IR LEDs. I have this circuit: PA12A to take the PWM 0-5 V control signal to limit the power supply to LEDs. The thing is even when the PWM ...
user avatar
5 votes
0 answers
89 views

Is this cascoded opamp structure unstable by design (LTspice)?

I am playing with a cascode op-amp design and I have problems judging its stability (schematic at the end of the post). When I judge the DC or AC analyses, it all looks good. No peaking and good phase ...
user avatar
  • 11.8k
-1 votes
1 answer
47 views

Adjusting output voltage feedback with a Howland Current Pump

I'm designing a variable bench power supply using the LT3790 IC. My requirements were adjustable from 1 V to 24 V in 10 mV steps, and a current limit adjustable from .05 to 5 A in steps of 5 mA. I ...
user avatar
0 votes
2 answers
103 views

Why is this op-amp outputting such low voltage?

Why am I not getting the expected gain out of my op-amp? I m using a 16-pin TI OPA4322SAIPW op-amp with a Advanced Photonix 019-141-411-R photodiode and this circuit: where Rin is 1.8 kΩ and Rf is 27 ...
user avatar
0 votes
2 answers
83 views

Need help to understand op-amp input resistor and capacitor network

I'm trying to understand the circuit design from this application note. Here is the figure: The author said: Resistor RIN provides a dc return path for the VS/2 reference voltage and sets the ...
user avatar
0 votes
1 answer
42 views

Current mirroring in diff amplifier

Hi , I tried to design simple current mirror (load) based differential amplifier. I was trying to make it for optimum swing limit. In the first image as you see I used an ideal current source . I was ...
user avatar
1 vote
1 answer
198 views

How to calculate op-amp circuit when there are two feedbacks?

I've got a question: how should I solve this? I've seen a thread were it was solved, but I don't know why the V+ is equal = V+ = Vout+(Vin−Vout)*R/(R+Rs) Like here: How are positive and negative ...
user avatar
0 votes
1 answer
34 views

Why does PMIC temperature increase drastically when opamp gain is increased?

I have an RF signal conditioning circuit that uses two AD8065 opamps for coarse gain. The board is powered via +/-12V, and is stepped down to +/-6V using MC7906 and MC7806 PMIC. The gain is controlled ...
user avatar
  • 653
0 votes
1 answer
84 views

Analog signal conditioning circuit selection for STM32F2 microcontroller ADC inputs

This is my first time designing an analog signal conditioning circuit for ADC inputs. The card will have up to eight analog inputs connected to eight STM32F207ZG ADC channels (stm32 mcu datasheet). ...
user avatar
  • 613
1 vote
1 answer
116 views

Eddy-current input to op-amp misses reading at times

The problem is only in the input stage of the op-amp. Edited: removed reference to "eddy-current" and changed to "reluctance". The reluctance-current is generated from two coils by ...
user avatar
  • 135
3 votes
3 answers
213 views

Feedback capacitor vs Miller capacitor in discrete op amp circuits

This is an overly simplified operational amplifier circuit with a feedback applied. The common way to make it stable is to add a dominant pole to the transfer function usually in a form of a Miller ...
user avatar
  • 569
0 votes
0 answers
47 views

Help understanding TL082 pre-amp/tone circuit

I am trying to construct a small 5W guitar amplifier with tone control as an introduction to audio electronics. I have taken two openly available circuits and I am trying to reverse engineer and ...
user avatar
-3 votes
1 answer
50 views

Cascading opamps to drive a MOSFET [closed]

I suppose, this is a continuation of this question: Parallelizing opamps for higher precision For the moment I'm leaning towards cascading opamps by implementing a Composite Amplifier, albeit a lazy ...
user avatar
-1 votes
1 answer
38 views

Compare same signal with different voltage thresholds using op amps [closed]

I would like to use two op amps to drive a transistor when receiving two different voltage ranges from the same input signal for a project. For example, I would like to switch the transistor on when ...
user avatar
  • 1
0 votes
0 answers
76 views

Slow slew-rate compared to the datasheet

I'm trying to create a 10 kHz PWM signal through use of op amps. In the output I'm using a TLV272IP op-amp working as a comparator: Since it has as slew rate of at least 1.8 V/us this should give a ...
user avatar
0 votes
1 answer
52 views

Impedance of buffered LC filters?

I am wondering if its possible to buffer LC filters? I am also wondering about the I/O impedance of the LC filters if you can buffer them. I do know the component values you pick for the LC filters is ...
user avatar
0 votes
2 answers
102 views

0 dB Bode plot as a reference in an academic paper

I want to compare the calculated bode plot of an inverting op-amp with the simulated one, on the 1 mHz-200 kHz spectrum. As expected, theoretically there is no stray capacitance on the circuit above, ...
user avatar
1 vote
1 answer
97 views

Op-amp wrong output

I have imported a Spice model of an op-amp from the link below and tried to plot the same outputs, but I am getting different results. Link to the Spice model I used and the desired plot: https://www....
user avatar
  • 45

1
2 3 4 5
143