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.

828 questions with no upvoted or accepted answers
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514 views

Make old telephone ring

I recently found one of those old rotary dial telephones in my garage and amazingly it still is fully functional (I tested it by hooking it to the phone line). As I have no use for it as a telephone ...
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1answer
211 views

Non-inverting op-amp saturating incorrectly

Background Hello, I'm trying to amplify an audio signal using an LM324N in a non-inverting configuration. I'm not trying to build an audio amplifier to drive speakers, I just need to amplify it a bit ...
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308 views

PIN Photodiode gamma detection amplifier circuit - rectangular wave output

I've been working on a project recently, where I need to build a device which detects gamma radiation and can be used for gamma spectroscopy. I've done some research and found many interesting ways of ...
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92 views

Need help with an IR demodulation circuit

I'm trying to reverse engineer a PCB and made a schematic. The bad thing is I only have PCB images from both sides, not the actual PCB. This PCB is used to detect a very small black object spinning at ...
3
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1answer
166 views

Opamp gain calculation

May be a very basic question, I am a chemical engineer with limited electronics knowledge. The circuit is a potentiostat with the current source \$I\$ being a sensor electrode. I was looking for a ...
3
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1answer
1k views

Norton Op-Amps advantages

I have been reading about Norton Operational Amplifiers, I get a good idea of how they work, even at the transistor level, I understand that difference current in = voltage output. What I have been ...
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138 views

Transimpedance AMP, Active HPF, phototransistor

So this is the part where I would like the phototransistor (TEMT6000X01) to be able to clearly capture an LED with a frequency flashing on and off at 1kHz. So what I have here is a transimpedance ...
3
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2answers
164 views

Measuring voltages from different sources sharing Common ground that might differ slightly

I have a design with resistor dividers and low pass RC filters dropping down 0-32V to ADC range of 0-1.8V. With multiple channels, I attempt to measure voltages from different voltage sources on a ...
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82 views

CA3140 wideband output amplifier

The following circuit is nearly exactly what I need for the output stage of my function generator: datasheet: https://www.renesas.com/us/en/www/doc/datasheet/ca3140-a.pdf What I don't understand is ...
3
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2answers
530 views

Opamp circuit stability (LTSpice)

I want to study the stability of my opamp 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 ...
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439 views

Piezoelectric transducer impedance and phase measurement

I have a circuit comprising of LT1210 current feedback amplifier (supply voltage = +/-15V, gain = 4) and its output is connected to a transformer (RM10 N97) with N=16.6 (150/9) which is further ...
3
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1answer
1k views

4-20mA current loop design

I have been working on 4-20mA transmitter project and stuck with a problem. My design is based on CN0319 evaluation board but I changed some of it, to make it works with other part of the design. ...
3
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3answers
349 views

Finding the transfer function of an op amp filter circuit

I have the following third order filter circuit: simulate this circuit – Schematic created using CircuitLab And I know that the transfer function looks like: $$\mathscr{H}\left(\text{s}\right)=\...
3
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2answers
269 views

ECG signal amplification

I am developing a project for ECG detection using PVDF (Piezo Film) sensor. I have already managed to detect my heart rate but since the sensor used produces voltage corresponding to vibrations, ...
3
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0answers
1k views

Peltier Driving Circuit

I am driving a peltier (thermoelectric heater/cooler) using a DAC (MCP4725), Arduino mega, quad-opamps to shift/invert the DAC voltage (LT1885) and 4xOPA549 (2 per peltier). I use PI control and ...
3
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0answers
894 views

Complete Noise Analysis: to find the minimum detectable signal of a TIA

Problem Statement: my aim is to digitalize a 10ns narrow pulse coming from a photo diode with current ranging from 10nA-70mA, as its impossible to cover this dynamic range of >60dB using a single TIA ...
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898 views

Deriving PI controller transfer function when input is reversed

I'm developing the compensator for the linear DC Bench Power Supply I'm designing. As I've come to deriving the transfer function for the op amp-based compensator, I realize I've been depending on a ...
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1k views

100kHz active filter design

I am designing a basic 100kHz active bandpass filter using opamps (LF353). I am only interested in receiving the 100kHz frequency (might drift a few kHz) from my input signal. I have used a basic ...
3
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1answer
460 views

Single supply op amp with input attenuator

I'm designing a guitar headphone amplifier that uses a single supply op-amp as the output stage to the headphones. I'm using a potentiometer after the final JFET stage and before the op-amps as a ...
2
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0answers
96 views

CW Doppler probe for fetal doppler and blood flow velocity

I am currently working on a microcontroller based project to measure the blood flow velocity using ultrasound doppler. I have purchased two Spengler 8 MHz continuous mode probes in order to measure ...
2
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0answers
40 views

two stage op amp's PSRR

I recently study about two stage amp. In Sedra-Smith, it stays that PSRR for VDD is very small, and ignores this. To understand this, I set Q6's source Vin and Q6 is acting like a common gate ...
2
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1answer
41 views

calculate op amp outputs problem separately

I was quite confused of this problem since I cannot find the Vo2 using KCL for Vo1 - Vo2 but in the problem, it just said dont use KCL for output voltage. Is it the way op amp operating or I am ...
2
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0answers
184 views

How to measure Common Mode Range and Output Swing of a CMOS Differential Amplifier in LTspice

I'm designing a CMOS opamp in LTspice here is my current design. The amplifier obtains a DC gain of roughly 50dB and has a phase margin of 70 degrees at a ω (unity gain frequency) = 250 MHz. I'm also ...
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394 views

How to represent a microphone using a voltage dependent current source in LTspice?

I am using the following schematic and I'm trying to simulate it in LTspice but I am not sure how to represent the microphone. My instructor said I should use a voltage dependent current source but I ...
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0answers
41 views

Differential communication, VCC and GND recovery

modern MCUs are consuming so little power that I started thinking about using only two differential data transmission lines for sending not only data but power also. I made a simple schematic below of ...
2
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3answers
87 views

Are these 2 circuits interchangeble?

I found the upper circuit. Originally it is designed as an output circuit for an audio player with a jack output. I have no transistora lying around, but opamps like the TL074. I made the lower design....
2
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1answer
68 views

Op-amp voltage on output during connection to constant current source

I'm looking to use an op-amp to control the voltage across a constant-current loop. To simplify things I think we can consider it a voltage follower. The constant current source provides 10mA, which ...
2
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5answers
182 views

TIA Photodiode SFH7050

I'm working with SFH7050 chip, it contains 3 LEDs and a photodiode. The datasheet suggests the next circuit: But it doesn't mention how to calculate Rf nor Cf. Which values should I use and how are ...
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0answers
53 views

Step response of Power amplifier

i have the parameters for this linear amplifier Swell rate >52 V/µs Bandwidth DC … 5 kHz Power 3 × 30 kVA rise time at nominal voltage (230 Vrms) is 5 µs. and the transfer function is: $$F(s)=e^{-0....
2
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1answer
94 views

How to explain the peak frequency and resistance relationship in this op amp circuit?

I was studying thid tutorial by Simon Bramble. I changed the original circuit a little bit and this is the subject of our discussion: As you see, R1, R2 and R3 are all 1kOhm. When I run an AC ...
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0answers
63 views

Crosstalk/Ghosting on ADC input

I have an ADC circuit which uses AD7689. The inputs of the ADC are driven by LT6010 opamp, and have a low pass filter . All 8 channels of the ADC (AD7689) have the same driving circuit. Every other ...
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0answers
90 views

Are there errors in the description of this circuit?

Background The circuit describes the operation of a variable voltage power supply. In the description below the circuit diagram there are errors. Read through the description and note down any errors....
2
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2answers
238 views

4 - 20 ma current loop, Short circuit isolator

I am trying to design a short circuit isolator, for 4 - 20 ma current loop based intruder alarm system.The below system,identify short circuit in sensing line and sensor activation(closing 1 k in line)...
2
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0answers
111 views

ADC in STM32F103 drops ouput voltage from unity buffer

I'm building a signal analyzer based on STM32F103RB6 placed on a noname board with the following schematics: I'm trying to normalize the AC input signal initially centered at 0V. The amplitude is 2....
2
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0answers
57 views

Audio amp IC: how does this output stage work?

I'm looking at an audio amplifier integrated circuit and the output stage seems a bit unusual. Has anyone seen this style of output stage, and does it have a name? And can anyone fill in the details ...
2
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0answers
113 views

Uniden BC780XLT Radio scanner, unknown modification

I recently purchased an old Uniden BC780XLT scanner. It has been modified replacing two smd resistor with THT resistors with different values. I am curious about this modification: what does it do? I ...
2
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1answer
214 views

In an inverting amplifier configuration why does do the gain resistors affect the circuit's frequency response if their ratio stays consistent?

I've been learning more about the characteristics of op amps and I found in a non-inverting amplifier simulation that the gain of an inverting op amp falls off as frequency increases. This behavior is ...
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0answers
50 views

TSM104W Voltage Reference

Hi I am trying to design with the TSM104W, which is a 4 package rail-to-rail OpAmps, with a built in voltage reference. This is the package pinout: I see that the four Op-Amps are supplied through ...
2
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0answers
65 views

First principles modeling of op amp CMRR

Introduction I'm trying to analyze an op amp circuit from first principles (i.e. without using the two rules of ideal op amp analysis -- virtual short circuit and infinite input impedance). The ...
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0answers
218 views

Comparator with hysteresis calculation

I'm trying to calculate the hysteresis of the comparator using currents but something isn't right. I'd like a little help to find the hysteresis thresholds without the simplified equations. simulate ...
2
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1answer
265 views

Using an op amp to balance a Wheatstone bridge by heating a sensor wire

I'm attempting to create my own hot wire liquid water content sensor, the control circuitry of which is similar to many hot wire anemometers: simulate this circuit – Schematic created using ...
2
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0answers
228 views

TLE2141 op-amp alternative (in DC load circuit)

I recently found a schematic for a DIY electronic load, which I think is based on Dave Jones's EEVBlog old DC load design (attaching the source link: Dynamic DC Power Load (updated), but I am ...
2
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0answers
73 views

Op-Amps in custom current limiter acting strangely

I'm building a small current limiter (~20 mA). It's important that there is little drop over the current limiter and that the load receives almost the full supply voltage when it's pulling less than ...
2
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0answers
31 views

Single supply analog gate current mode switching

I need to switch a bunch of analog signals, in the \$\pm10\$ volt range, with the control coming from a microcontroller. Since the signals are all ending up in the virtual ground node of an opamp, I'm ...
2
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0answers
313 views

How to connect Electret Microphone module and OPAMP?

I am trying to build a circuit that gets electret microphone input and maps into 0-1V for utilizing in ADC. The microphone module suggests using such circuitry When I tried that circuit and talked ...
2
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1answer
427 views

Clipper circuit in OpAmp

I came across this clipper circuit: I was analyzing this circuit. I could not very clearly understand what is the purpose of resistance, R here. I understand that if we do not include this resistor,...
2
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0answers
66 views

Improve the frequency of Current Source Howland effect Op-Amp

I need help on a Howland Effect circuit with a current source purpose with an output of 600mA and a constant gain throughout a range of frequencies starting in 0Hz to 1Mhz. I am currently using an ...
2
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1answer
212 views

Slew Rate, Settling Time, Bandwidth, Rise Time - High Speed Transimpedance Amplifier Design

I'm in the process of designing a Transimpedance amplifier for an analytical instrument. The sample waveform (hand-drawn) is attached in the attachments. The requirement is to amplify a pulse kind of ...
2
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0answers
128 views

Choice of passive components for AD549/AD630 low-noise circuit?

I'm trying to reproduce an "ultra" low-noise amplifier circuit which calls for several precision amplifiers/modulators (AD549/LF356/AD630). The input source is a Hamamatsu S1223 photodiode capturing a ...
2
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0answers
189 views

How does an op-amp work without proper power supply?

I have built a chua's circuit following this diagram: Source: Kennedy 92(pdf). The rectangle inside NR is and eight pin dual opamp. Then, I remove the 9V battery on the right. It is replaced by a ...

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