Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers,

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1answer
23 views

How to calculate the input impedance and transfer function

I have the following circuit, that is used as a signal conditioning circuit in a audio system project. I am trying to calculate the transfer function and the Zin(input impedance) and Zout(output ...
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2answers
27 views

Why does my diode log amplifier in LTspice not match theory?

I am trying to learn about analog multipliers, and I'm trying to implement one using a log-antilog design. I am currently having some difficulties with the log part because simulating an ideal ...
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2answers
35 views

Low crosstalk opamps (Burr-Brown)

I stumbled across some information about an opamp on the Texas Instruments Site, the OPA1604 and in the datasheet it says: These devices also feature completely independent circuitry for lowest ...
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1answer
38 views

Where do input bias currents flow and what voltage drops do they create?

I have asked this question (and answered it below) mainly as a continuation of the question, How does the compensation resistor in an inverting amplifier compensate for the input bias current?... but ...
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2answers
87 views

What is the bode plot of an inverting op amp if you replace the resistors with caps?

What is the bode plot of an inverting op amp if you replace the resistors with caps? What if you now add a capacitive load to the output? Update: I ran a quick simulation and the bode plot looks as ...
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0answers
34 views

Transimpedance opamp specification

I am trying to design a circuit that measures a sensor that outputs 20nA to 2mA. I only need to read a sample per second so slow. I need to know what should I look for when I search for opamp that is ...
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1answer
81 views

convert pwm to analog signal with a load of 0.7A

I have a question, an easy one I believe. I am designing a small module which may take control of an analog model train as soon as the train is detected. When the train is detected, a uController must ...
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4answers
225 views

Switching gains on a precision operational amplifier using a microcontroller

I need to be able to switch between gain values on a precision opamp in the microvolt region using a MCU. What is the best method to do this? Noise is critical.
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1answer
38 views

Read voltage / tap into existing voltage divider circuit without affecting?

I'd like to unobtrusively read the voltage of a simple thermistor & voltage divider circuit. This is a hot tub/spa controller and it is using 5v -> 20k (R1) -> thermistor (R2) -> ground ...
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1answer
30 views

Open-Loop Gain and differential gain

Assuming an op-amp that is connected without any feedback. Then in theory does Open-Loop Gain and differential gain convey the same information or am I missing something?
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2answers
44 views

Unable to connect amplifier output to comparator in opamp

I am amplifying a signal for a current transformer (CT) with an op amp. This amplified output signal I need to compare using op amp comparator. The supply voltage is 12V and the IC is an LM358. When I ...
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1answer
27 views

1-5V to 4-20mA current loop transmitter

reference:https://www.analog.com/media/en/technical-documentation/technical-articles/D61_EN-Convert.pdf The above circuit take input voltage of range 1-5V and gives the corresponding current output of ...
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2answers
52 views

Op AMP UA741 Issue

Can anyone suggest me a simple circuit to shift a 0V/5V sine wave (low freq, under 50KHz) to a sine wave -2.5V (when was 0) to +2.5 (when was +5V). I have used a circuit for shift a 0V/5V sine wave (...
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35 views

Layout polygon pour connect to GND or VGND noise reduction

I am using MCP6V02 as transimpedance amplifier as shown below schematic, I want to know is it better to connect polygon pour to GND or VGND to reduce noise on the amplifier. (Below schematic is for ...
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1answer
53 views

Does the formula \$Av\times \left( v_{in-}-v_{in+}\right) \$ of opamp applies also for DC voltage input?

For a two-stage Miller op-amp, if I only apply DC common mode input, the vout is obviously not zero, since there is a voltage drop across M7. So does this mean that the formula Av*(v_in_plus-...
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1answer
38 views

Sensor input calibration for wider range

I get minimum voltage output from my sensor as 2.2V and max voltage as 2.65V. I want to change this voltage to 0-5V range so that the controller ADC can calibrate input in a wider range. How can I do ...
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0answers
37 views

Back-to-basic question regarding OpAmp, its input and output information

I am doing literature research about Transimpedance Amplifier (TIA) architecture and designs. What I know for sure are its input is current, its output is voltage and it has low input and output ...
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1answer
52 views

Over voltage and reverse voltage protection of analog input circuit with voltage follower

There will be 8 analog signals read by a microcontroller (STM32).I want to design a protection circuit for analog input. The input can be 0-10V or 4-20mA controlled by the MCU using an inverter based ...
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2answers
54 views

Lead resistance of 3 wire RTD100

I am using a three wire RTD100 as a temperature sensor. I know the advantage of the 3 wire RTD100 is that it gives accurate temperature output by canceling the lead resistance. First the resistance ...
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3answers
259 views

How does the compensation resistor in an inverting amplifier compensate for the input bias current?

I can't see how a resistor placed on a whole other input terminal has anything to do with compensating this input bias. i.e. the input stages are just the gates of transistors of differential stage. ...
2
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1answer
55 views

Why doesn't the negative feedback current in an op-amp inverting amplifier drive the op amp into saturation?

I know the rule that states that the negative feedback will keep the difference in potential between the inverting input and the non-inverting input (almost) zero. Now I just wanted to take a moment ...
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1answer
93 views

Simulation isn't working for high voltage amplifier

Been trying to simulate on multisim a circuit I saw about high voltage amplifier: The input is 8 Vp-p and 100Hz and reached to output of 1800 Vp-p and 100Hz. The publisher mentioned he used the ...
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2answers
38 views

transimpedance amplifier based on a capacitive feedback current amplifier

I am trying to understand the circuit in this publication. The picture below is the simplification of the circuit. I do not understand the role of the cascode configuration part of the circuit. ...
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6answers
2k views

How do professional designs compensate for offset voltage in opamps?

I am new to electronics and have been told in class to always add precision potentiometers to compensate for input offset voltages in opamps for signal conditioning. My concern is that this offset ...
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2answers
53 views

Temperature sensing with ADS1115

I am using an ADS1115 as an analog to digital converter to measure temperature. I am using an RTD100 temperature sensor to measure a temperature range of -40 to 150 degree celsius but the resistance ...
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1answer
41 views

how to know where to put the threshold signal of an op-amp comparator

I am really confused on where to place my signals on amp. So basically what i want is a comparator that when a Vsignal exceeds Vthreshold the output would read HIGH on the GPIO. My Op-amp is TLV7041 ...
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2answers
49 views

Trimming a power supply to 0 V output in current limit

Here is another question on the originally Czech bench power supply that I recently built, but in the version¹ of it sold by various places (e.g. eBay) very cheaply. The circuit has two potentiometers ...
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2answers
81 views

Maximal Cable length for a given Opamp

How can one determine the maximal cable length an Opamp can drive without getting unstable? The thing which leads me to this question is that the impedance of a cable changes over frequency. Means, a ...
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2answers
78 views

Modifying an op amp filter to use single supply

I'm having much difficulty modifying a "state variable" bandpass filter from being dual supply to single supply. (https://www.electronics-tutorials.ws/filter/state-variable-filter.html) Here ...
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2answers
56 views

What does a TL062 Op-Amp with output grounded and both inputs connected together with voltage divider mean?

So I'm studying Kilovoltmeters and subsequently using ADC's with resistor arrays and dividers from high voltage power supplies of all varieties. I've got a good idea as to what they are and how they ...
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1answer
35 views

Signal distortion in simulation of a current to voltage converter

I'm trying to simulate a current-to-voltage preamplifier as part of a circuit I'm building. The current signals I'm working with range from pico-amps to nano-amps. With a gain of \$10^8\$ ohms, a 50 ...
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1answer
39 views

Level Shifting Circuit to output 0.2V-4.8V

Having a sensor's dynamic range from 4V - 10V, I am looking for a level shifting circuit using op-amp that gives me an output of 0.2V - 4.8V. I have been looking through many design yet I could not ...
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1answer
28 views

Right approach to boost the current of a signal to drive a speaker

I have a circuit which can produce three different waveform signals ( Square, Sine and Triangle). The output amplitude of these signals goes from +5V to -5V Peak to peak. However the output from this ...
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2answers
63 views

Op-amp unity gain buffer introduces distortion in the LM386 circuit with high gain factor

I'm building a simple mixing stage, lowpass filter, and final amp in sigle supply (9v battery). I started from the LM386 circuit on the data sheet. It had a lot of distortion which was solved with the ...
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1answer
40 views

ua741 DC offset on the output

I have ua741cn and connected it to 10V. V_+ =10V V_- =GND Just to verify I have a valid chip I did a little test. I connected the non-inverting input to GND and the inverting to 10V I would expect the ...
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1answer
64 views

Applying a forward bias to a photodiode to shift output

I am using this TIA circuit and photodiode in photovoltaic mode. I'd like to modify the circuit such that at zero light a positive voltage is produced at Vout. And as more light falls on the ...
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2answers
90 views

How to find a Pin-to-Pin Replacement for TL-081, but with higher VCC? [closed]

After ordering and assembling one of those¹ "red" 0-30V/0-3A power supplies from eBay/AliExpress and taking a bit of a closer look at it, I'd like to replace the TL-081 op-amps. It's working ...
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1answer
39 views

Do I still need tweaking after using gm/Id method if some of the MOSFETs are not in saturation?

gm/Id method links the design spec to gm, width, Id of each MOSFETs. There are some design examples that show how gm/Id is used in the circuit designs. They show the sizes of the MOSFETs and how it ...
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35 views

Inverting Op Amp Finding resistor value of voltage divider

A small clarification V_2 = -100V_1 I don't think my analysis is correct since I ended up with R1 as a denominator.
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2answers
50 views

how does this op amp circuit 0-10V converter work?

This circuit is supposed to be 0-5V to 0-10V/4-20mA converter. I know that : R7+C1 forme an RC filter R5+T2+R4 an inverter to switch between 0-10V and 4-20mA in output the Op-Amp is working as ...
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1answer
55 views

Noise generated in 2nd stage of active bandpass filter

I'm breadboarding a two-stage inverting amp/filter to amplify a radar signal, using the TLV2464 opamp. My first stage has a gain of 45dB, the second stage 35dB. The input will be a radar signal which ...
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2answers
64 views

How Can I Design a Non-Inverting Active High Pass Filter?

All the active filters I've found 0n books and google are inverting type (i.e. input signal is applied at the negative input pin of the op-amp). I thought if I apply the input signal at the positive ...
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0answers
37 views

differential Op-Amp oscillation

I have used the THS4151 op-amp to create a circuit that takes two inputs and subtract them to give an output. Below is the schematic for the circuit: R1 is where I will input a 1 MHz, 2V sinusoidal ...
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1answer
26 views

DC offset in closed-loop ideal op-amp

It's from Sedra. It's about how the offset current messes with the input of an inverter. It's "easily seen", but no so for me. Can anyone explain to my "not easily seen" brain how ...
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1answer
102 views

My FM transmitter never works, Why? [duplicate]

I'm trying to build a FM transmitter, but without sucess. The current schematic I'm using is this one: The alternating current at the (+) of the op amp is the P2 output of my phone. V3 and V4 are 2 ...
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1answer
67 views

Opamp: Compensate to achieve constant gain

I have been trying to achieve a constant gain across an LM318 opamp in a differential amplifier configuration ranging from 500Hz to about 500kHz. The opamp has a bandwidth of 15Mhz. Since the gain is ...
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2answers
35 views

How to use an op-amp (that only uses ground and positive voltage to operate) to create a sawtooth/triangle wave generator?

The design I have in mind will be battery operated, so I have found the TL972 (Datasheet Here) which only operates from 0 - 12 V. What I want this op-amp to do is to create a sawtooth/triangle wave ...
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1answer
39 views

DC residual current detection 24 volt DC

I am trying to make a DC residual circuit breaker( same as AC 10 mA RCCB) for 24 volt DC load. How can I sense and compare currents in positive and negative terminals and powering circuit off, a ...
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1answer
61 views

differential to single ended output problem

I have a differential input of 2-V and it apply to TLV-2221 op-amp with unity gain of one, but the output shows the zero voltage waveform,can anyone explain why it happens? here i am attaching the ...
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0answers
59 views

op-amp output problem

I am using the TLV221 opamp for differential to single ended output with unity gain of 1. In simulation, we didn't get the expected output. The output of the AMC1301 isolation amplifier is 1.98V so ...

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