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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2 answers
2k views

Op amp buffer output voltage offset

I am building a system which will measure and record the voltage of batteries. There are 8 channels in the system with each channel being capable of measuring 0-35 V. The accuracy we have decided upon ...
2 votes
1 answer
32 views

op-amp simulation

I am not sure what's the mistake I am making on the below simulation. Below is a Non-inverting op-amp (IC Link) with Gain as 3. Case1 : Input: 1MHz; Offset:0.5V; Pk-pk Amplitude: 0.2V Result: The ...
8 votes
3 answers
409 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 ...
3 votes
1 answer
70 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 ...
3 votes
2 answers
1k views

Op-amp circuit stability (LTSpice)

I want to study the stability of my op-amp circuit with LTSpice. I found this video as tutorial: tutorial on phase margin So, I did the simulation with closed and open loop as suggested and got the ...
0 votes
1 answer
781 views

Making block diagram of an op-amp configuration

Hi everyone, I have to make the block diagram of the above configuration. Supposing the input capacitance of op-amp Cin, I've drawn this: A is the open loop transfer function of the OPA. B is the ...
0 votes
1 answer
45 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 ...
2 votes
3 answers
153 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 ...
0 votes
2 answers
275 views

Series voltage regulator op-amp

I am using LTspice trying to find out the extremums of tbmhe output of the following circuit. The diode, op-amp, and PNP transistor are the default components. What I know at the moment is that \$V_{...
0 votes
1 answer
56 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 ...
0 votes
3 answers
115 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, ...
0 votes
1 answer
951 views

Does anyone have an STM32F example for opamp PGA mode (ideally STM32F3 Discovery)?

Ive used STM32cubemx to set input pin and output pin of OPAMP1. Then open project in Keil and I can see the OPAMP functions are loaded and compile OK. But when I load code into MCU (STM32F303 on ...
1 vote
0 answers
54 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 = ...
0 votes
2 answers
44 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 ...
4 votes
4 answers
298 views

Unity-gain bandwidth circuit with uA741 op-amp

Q: Using Op-Amp uA741, design an amplifier that offers a passband gain of 40dB with a minimum bandwidth of 20kHz. The current through any resistor in the amplifier should not exceed 10 mA. Include the ...
1 vote
3 answers
94 views

Buck converter adjustable output-voltage using digital potentiometer

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 ...
0 votes
2 answers
78 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 ...
0 votes
1 answer
54 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 ...
1 vote
1 answer
305 views

Transient Response of AC Coupled Inverting Amplifier

The circuit below is from this App Note. The document describes: The capacitors C1 and C2 need to fully charge for the circuit to function properly. The definition of fully charged can vary depending ...
1 vote
1 answer
206 views

Questions from a current regulating and measuring circuit

In my previous question I asked about a simple topology suggestions for regulation of highish currents(around 10A) especially for resistive heating elements in 1...10 Ohm range. I concluded to use a ...
0 votes
1 answer
83 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). ...
1 vote
1 answer
35 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 ...
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 (...
-1 votes
1 answer
45 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 ...
4 votes
3 answers
267 views

Problem with simple non-inverting NE5532 configuration

I am building a small amplifier which is working just fine. While experimenting I interchanged the TL072s with NE5532s and the amplifier stopped working, so I set up a simple non-inverting amplifier ...
0 votes
1 answer
33 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 ...
1 vote
1 answer
115 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 ...
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 ...
0 votes
2 answers
102 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 ...
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 ...
0 votes
1 answer
41 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 ...
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 ...
1 vote
2 answers
191 views

DC signal to Integrated signal for analog filter circuit

I'm new to analog electronics, and I am stuck on one issue. Let's say I have an input signal, like blue one: To get a DC form I can rectify it (got a grip on it.) What I need is a smooth (regulated) ...
1 vote
2 answers
3k views

Second order all-pass filter using a single op-amp

Is it possible to build an active second order all-pass filter using a single op-amp and no inductors? After Googling it I've found no less than three different circuit topologies, but when simulating ...
1 vote
1 answer
139 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 ...
0 votes
1 answer
674 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 =...
0 votes
2 answers
148 views

I am trying to build a waveform amplifier and having no luck

I am trying to build a waveform amplifier with a gain of 10 to amplify the voltage coming from a signal generator because its maximum output is 10 Vpp. The simulation works: As expected, I am seeing ...
0 votes
2 answers
101 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, ...
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 ...
0 votes
2 answers
998 views

Triode preamp with TL072 phase inverter buffer?

Wondering if anyone can advise on this tube triode (12ax7) preamp stage followed by an Op Amp buffer stage to correct the inverted signal. I wired it up and did not work. Before tho, I wired it with ...
3 votes
3 answers
210 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 ...
0 votes
0 answers
45 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 ...
3 votes
3 answers
624 views

Simple version of an internal op-amp circuit

I'm currently learning how op-amps and transistor circuits work and want to understand the simple version of an internal op-amp circuit. However, there are still some open questions. The first stage ...
-3 votes
1 answer
49 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 ...
0 votes
2 answers
1k views

Photodiode circuit Op Amp and amplification failure

I am trying to build a photodetector circuit to detect and amplify the output signal of a fiber laser. I started with testing my fiber pigtailed photodiode on a breadboard as shown. simulate this ...
0 votes
1 answer
240 views

Resistance Conversion/Scaling Circuit [duplicate]

I'm looking into building a custom gauge cluster for a project truck. The fuel level sending unit that I have will read 40 ohms when the fuel tank is empty, and 250 ohms when the fuel tank is full (it'...
0 votes
0 answers
74 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 ...
-1 votes
1 answer
37 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 ...
1 vote
3 answers
207 views

Current Source Output Does Not Become 0

I put a simple current source on a circuit to drive a UV LED with a constant current. According to the LTSpice simulation setting 0 V at the signal input results in 0 A through the LED. But when I ...
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 ...

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