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
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1answer
72 views

How to feed reference voltage for two op amps inputs with different input signal each one

Im building a Stereo Buffer and a Baxandall circuit together. In powering the circuit with a single supply of 9v, and i need to bias each four inputs with 4.5 volts. The question is: If i feed the ...
3
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2answers
393 views

Why does LM324 Op-amp send out max voltage when I got 0V at the non inverter input?

I have this circuit. The goal is that it going to control the current loop by using the NPN-transistor. My problem here is that 0V results that the output from the Op-amp is near 24V. Why? If I'm ...
0
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1answer
86 views

Why OpAmp is designed to have a cut-off frequency 1 kHz, but indicated Op Amp respond to sinusoidal input of 10 kHz?

An Op Amp is designed to have a cut-off frequency about 1 kHz, a circuit designed with the indicated Op Amp is able to respond to a sinusoidal input voltage at 10 kHz. How is this ...
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44 views

integrator outputing velocity

I'm trying to make a integrator output the velocity receiving an accelerometer signal based on the next design But the output seems to be fixed on a certain level as showed here I'm thinking the ...
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1answer
43 views

Op-Amp Input Common Voltage Range for specific gain

This is the circuit I am working on. I am using this instrumental amplifier AD623 with a gain of 100 using a 1k resistor between pin 1 and 8. (https://www.analog.com/media/en/technical-documentation/...
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0answers
43 views

Op-Amp and foldback limiting of voltage power supply

I am new in forum. Can an opamp which drives a small load and whose output current exceeds the maximum output current of the opamp cause a foldback limiting of the power supply? If I use a class ab ...
3
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3answers
393 views

Differential Opamp: How to cut or reduce current consumption from supply rails

I built a simple differential amplifier using an LM358: Please find the datasheet here I want to reduce the current consumption so my idea was: Use a GPIO pin of my MCU to switch Vdd supply to the ...
0
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2answers
110 views

Op Amp confusion

I have the following curcuit that converts a pulse train from 0 to 5V range to -5V to +5V range. My bandwidth is 1MHz. OK so far so good & apologies if this isn't an appropriate place for the ...
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1answer
52 views

Op-Amp Impdance Question

For the problem shown above since there is no current travelling through the input of the Op-Amp can we assume that the Op-Amp is acting ideally? And using this assumption can we ignore the output ...
1
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1answer
56 views

Output Resistance of Small-Signal MOSFET Circuit

I have some doubts concerning the calculation of the small-signal output resistance of a common-source stage with source-degeneration. This is related to another question I posted but I have refined ...
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0answers
51 views

Balanced to unbalanced circuit not working correctly?

I've tried to build a balanced to unbalanced signal converter with an TL072. The problem is that if I put a balanced sine signal into it I only get the bottom half of the sine as unbalanced signal out ...
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0answers
22 views

Dual tracking PSU: how to derive set voltage for second “half”?

I'm fiddling aroud trying to design a dual tracking PSU, based on the LT3080-based design by eevblog/Dave Jones. The general idea is to use a microcontroller obtain \$V_{set}\$ in the range of 0-2V, ...
3
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3answers
298 views

How can I do two points scaling in electronics? 0.6 V - 3.2 V to 0.0 V - 3.3 V

I'm seeking a solution how to do a two point scaling in electronics. I have tried an Op-amp, but it did not work very well. So I wonder if you have some ideas how to do two point scaling from e.g 0.6 ...
0
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1answer
40 views

Controlling wave amplitude by arduino

I built waveform generator using AD9833. It can produce sine and triangular wave with amplitude about 1.6 V and square wave with amplitude of 4.5 V. I'm searching for some circuit which can control ...
0
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1answer
38 views

How can I find the slope at Vout/Vin at Vin = 0, from the datasheet about Op-amp?

I'm trying OpenModelica and I'm going to simulate an Op-amp. (No it's not Windows 95, it's IceWM + Ubuntu 20.04) But I wonder where I can find the slope Vout/Vin when Vin = 0 in the datahseet? I have ...
1
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1answer
72 views

Does this Buck-converter work?

I am using the buck-converter circuit from Low side N-Mosfet buck converter as the base of my design. And I want to replace the diode with a P-channel MOSFET. I also want to drive both MOSFETs with an ...
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1answer
62 views

Need help with low power audio amplifier circuit [closed]

I intend to output an 8-bit waveform generated on an ATtiny1614 microcontroller running at 3.3 V to a 1-2 W, 4-8 ohm speaker and have the user able to change the volume. For that, I am thinking about ...
1
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1answer
73 views

Understanding why an OPA27 is unsuitable for a window comparator and a MC1458DR is better

I'm a junior electronics engineer and have a question about a window comparator circuit I've built: Circuit Explanation: The op amps have a tight reference voltage on their non-inverting terminals. ...
0
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1answer
72 views

Analog circuit for a photo sensor

I'm personally developing an analog circuit for a photo sensor using very cheap op-amp. My biggest motivation for my circuit is to design it cheaply as much as possible. My main op-amp is a TL071. ...
0
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1answer
54 views

Potential In VA

I'm trying to find VA and I don't get something, is Ic1 = V+/20k, and then this current splits through emitters of Q1 and Q2? If so, then the voltage VA is 0? Also, I know that Q3 and Q4 are a ...
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0answers
25 views

EMI cause dc offset on Opamp output

I have issue where opamp output shifted when I connect the chassis to Earth ground, I want to know what is causing this and how to prevented. (main pcb never connect to earth ground just external ...
0
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1answer
44 views

op amp random pulsing to ground

I have simple circuit with ada4891 op amp. I am using it to demodulate ASK modulated signal. But sometimes op amp is pulsing to ground for no reason. These pulses are short (about 1 us). I have ...
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0answers
25 views

LMH6629 Spice Model, where to put compensation pin?

I am trying to use a spice model from TI for the LMH6629 op amp and the model has a compensation pin. I pasted the code in a spice directive and tried to use a generic op amp model for it, but the ...
1
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1answer
52 views

Current direction in a multivibrator

I have been studying multivibrators lately, but I have hit a wall right now. I have attached a sketch for an astable multivibrator. I know the basic stuff. When Vout is high then Vin will rise as CT1 ...
3
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2answers
58 views

Not accurate readings when connecting OpAmp AD822 to ADC MCP3008

for my project, I am using a photodiode, that I connected to the AD822 OpAmp. This OpAmp should then be connected to the MCP3008 ADC. I am reading the data from the MCP3008 with a RaspberryPi. I am ...
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0answers
39 views

Set feedback fraction of inverting input configuration

Suppose we have this: simulate this circuit – Schematic created using CircuitLab How can we set the feedback fraction of this closed loop configuration?
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1answer
48 views

Op Amp with capacitive load - Peak Detector

I have been looking into peak detector circuits for something I am designing and looking through Google, the common method seems to be this: Quite simple really. But, I have an engineer at my work ...
4
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1answer
42 views

DAC/ADC Precision & Noise: PD Resistor/Capacitor effect

I'm developing a device that utilizes both ADC and DAC, and I have realized that my DAC output, which is fed into the op amp, is de-facto almost floating, since op amp has high input impedance. Both ...
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0answers
61 views

Wien bridge oscillator frequency

Question from Microelectronic Circuits by Sedra and Smith, Section 17.2: Op Amp–RC Oscillator Circuits: 17.10 For the Wien-bridge oscillator of Fig. 17.4, let the closed-loop amplifier (formed by the ...
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2answers
106 views

Could someone explain to me a simple opamp problem, please? [closed]

Could anyone please explain to me why a simple voltage follower misbehaves in certain configuration: Opamp LM358 configured as voltage follower. Working case: Vcc 12V. +IN: pulled up to 5V with 10k ...
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3answers
89 views

Small AC-DC conversion/amplification

So essentially looking for the most efficient and effective way to take a 3V 50hz AC signal and convert it to an 11-33V DC signal (any voltage between 11 and 33 works for an input to embedded pc) . I ...
1
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1answer
44 views

Weird hysteresis behavior

I am an EE student and recently we worked with Schmitt triggers, positive feedback loops, and hysteresis. I was curious and hooked up an mcp601 without a feedback loop as such: In the above schematic ...
1
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2answers
78 views

Bad on output of Constant-Current source

What I'm trying to do? I'm making a constant-current source based off an existing design. The specs of the existing design are: Existing Design The design is of a constant current source capable of ...
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3answers
456 views

Op amp output limited [duplicate]

I'm playing around with this op amp: https://www.st.com/resource/en/datasheet/ua741.pdf. My circuit looks like this: It is hooked up to an Arduino Uno. I used analog read on the Arduino to read ...
0
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2answers
47 views

How can I create feedback measurement with an operational amplifier? 0-20mA measurement

I want to build something like this. This circuit controls 0-20mA but the circuit have one big problem. If the circuit load e.g 100 Ohm changes to e.g 200 Ohm, then less current is going to flow. To ...
3
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3answers
278 views

Input Impedance of the Inverting Op Amp

I'm having a hard time understanding how to calculate input impedance of the inverting op amp. First, which two points do I need to calculate the impedance between? Is it between the two points ...
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2answers
87 views

op amp with capacitors

Why is Cp here not part of the equation?
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0answers
30 views

Nodal analysis/op-amps question

In the question above, are we deriving based on the equation which uses resistors, shown below? Why is it inverted, i.e. $$C_f$$ is below instead of above? If so, why is $$C_p$$ not factored in the ...
2
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2answers
144 views

What is the purpose of the anti-parallel diodes in this Wien Bridge oscilator circuit?

In the following op-amp circuit: Rf here is replaced by the following: What do the anti-parallel diodes here serve? This is a Wien Bridge oscillator circuit and I am showing only the negative ...
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0answers
72 views

Ferrite beads as power rail in opamp breakout analog input circuit

i'm designing a small breakout boards that is used to interface some external sensors (voltage and current) to a MCU. In order to get better results, i'm using an external dedicated ADC, the ADS1115, ...
2
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2answers
145 views

Design of high voltage MOSFET amplifier

I need some hints in designing a ±300 V amplifier stage. The output stage should be two MOSFETs. The current needs to be very low for now (about 50 mA). The bandwidth is not so important for now. The ...
0
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0answers
56 views

Op- amp comparators and temperature dependent resistor

The circuit in Fig 1 consists of a temperature dependent resistor (TDR). Compute the: temperature at which the comparator will change state. 2)supply voltage required for a 40°C trip point in Figure ...
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 ...
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1answer
40 views

Strange problem with differential amplifier for current sensing with TL084

I have a problem with the circuit below: I'm using the op-amp as differential amplifier for low-side current sensing with gain of 100. All resistors are 0.1% and the load is just a variable resistor ...
0
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0answers
58 views

Transimpedance amplifier transient voltage issue

We have below transimpedance amplifier, I have below issues, would like to know if this is even fixable or could be reduced: When a large load turn on in main power supply of TLE2426 turns on cause ...
2
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2answers
106 views

Why is Arduino Uno Rev3 input voltage specified up to 20V? OpAmp

The Arduino Uno Rev3 has an OpAmp (TI LMV358IDGKR datasheet) where the non-inverting input ("CMP") is connected via a voltage divider to Vin. The OpAmp's supply is connected to 5V. On the ...
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1answer
50 views

Reg opamp circuits with no input signals

In circuits where there is no input signal shown explicitly as in the figure shown below, how do we determine the behaviour of the circuit? I understand that the power supply given to the opamps ...
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0answers
54 views

AC signal gets unwanted DC offset when connected to circuit

Hi im a 4th year ELE student and I am creating a circuit which outputs 120khz square wave burst when it detects zero crossings from the input ac signal. Here is the circuit diagram Op amp 1 converts ...
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0answers
65 views

Battery Capacity Tester - Schematic Review

I designed a circuit to test Lithium battery (3.7v) capacity. My measurements do not need to precise but should be relatively accurate between each batteries so think this should do. Schematics: Using ...
3
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3answers
150 views

How to analyze this opamp circuit?

So with the following circuit (currently studying for an exam): I am able to get V- just through the voltage divider composed of 2R and R at the non inverting terminal. However, once there, I am ...