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Questions tagged [op-amp]

An op-amp (operational amplifier) is a high gain analog voltage amplifier with differential high impedance inputs, and a low impedance output. A basic building block in signal processing, like as amplifier or active filter.

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Differential amplifier with common voltage far above the rail?

I have a thermocouple with one end connected to +24V. I want to be able to read the voltage (-5mV - +20mV) on it using a 3.3V ADC. The most reasonable solution I see is lowering the voltages using ...
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43 views

Correct use of op-amp to amplify photodiode in reverse bias

So I have a photodiode in reverse bias, from which I intend to measure my pulse. Currently, my schematic looks as follows: simulate this circuit – Schematic created using CircuitLab Weirdly,...
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1answer
55 views

Input impedance of low pass filter on LTspice must be constant in it's pass band?

I have single supplied sallen-key filter more that have nice 3MHz flat LPF response. I tried to compute the resistance directly by dividing the input voltage by input current which is the voltage and ...
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24 views

Add OpAmp subcircuit spice model to Altium

I want to add SPICE OpAmp model of Analog devices by .cir extension containing .SUBCKT information to Altium. I have it's schematic but I don't know how to add it's simulation file to it. I have ...
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3answers
95 views

Determining Impedances of an Op-Amp Circuit

I'm trying to review some old concepts, and thus far, there was one that I couldn't really understand: impedance of circuits involving op-amps. Assuming an ideal op-amp, it has infinite input ...
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44 views

I want this problem solution [on hold]

please i want the solution of this problem i tried to solve it but no answer. Calculate the maximum achievable bridge deflection voltage for an applied torque T
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0answers
29 views

Queryable open electronics database for e.g. op-amp parameters [on hold]

I often want to make complex parametric searches for components, particularly op-amps. The large component sites like RS, DigiKey, etc. allow basic queries via their websites, but these are usually ...
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96 views

Is there current flowing through this capacitor?

Let's say \$ V_s \$ is some time-varying voltage source. Is it necessarily true that the current going through \$ C_1 \$ is zero? I would think that the answer is yes, because the current flowing ...
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21 views

Q: Unexpected behavior from digital Rheostat

I have no idea whats warranting this behavior from the MCP4162 device Starting from 500mV(pp) - 2.8V(pp) a weird "wave" like distortion happens in between the two voltages. (Towards the negative ...
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1answer
102 views

Is static negative resistance practically available?

I learned that negative resistance (NR) could be simulated by involving active devices like op-amps and others. I'm interested in the static/absolute NR rather than the differential NR. My question is ...
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1answer
42 views

Voltage on LM4140 Vout

I'm using an LDO called LM4140 with an op amp, where VREF is connected to the output of an Op-amp via a resistor network. As the op-amp will be outputting voltages from -10v to 10v, is there any ...
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50 views

Help deriving the differential equation of an op-amp circuit [on hold]

derive the differential equation relating the output voltage to the input voltage of the circuit given below, and indicate the expression for the time constant.
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26 views

touch operated relay using op-amp [on hold]

I have a project that requires a circuit of a touch operated relay using op-amp. my problem is i don't have enough knowledge to achieve it. i tried to look for it a lot but could not find any ...
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2answers
46 views

op-amp pin is sitting at high voltage (active low-pass filter)

I am looking at using the OP1177 to act as an active low pass filter. I need to smooth out a 20kHz signal burst with a minimum of 50 cycles to reach a voltage on the output to interrupt an ...
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1answer
668 views

What is the purpose of op-amp in the output of Instrumentation amplifier

I encountered a problem while solving an analog circuit. I just need to know the purpose of the last op-amp (K4) at this circuit: while solving I understand it just amplify the output voltage from ...
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1answer
78 views

Need help getting at least +/-10 V from op-amp

I'm new to here and I did already some of the research but cannot really find an answer. I'm not very familiar with op-amps. I have wired a LM358 op-amp as per the below example schematic in the ...
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1answer
61 views

Telescopic cascode operational amplifier: why not rail the bias nodes?

In a fully differential telescopic cascode opamp, there is a bias voltage for two of the nMOSFETs whose gates are tied together and a bias voltage for two of the pMOSFETs whose gates are tied together....
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1answer
55 views

Potentiometer for TL081 [on hold]

What kind of potentiometer (resistance) would be suitable to connect to the Offset pins on the TL081 Op amp, when used with +/-15V? And if I choose to omit the pot altogether, roughly speaking, how ...
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1answer
37 views

Opam circuit where Vout =(V11/3 + V25/2)1/3

Hi i need to design an opam circuit where But I can't find anywhere where I can get exponential outputs can you please help!
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1answer
26 views

High Common mode op amp shunt compensation

The High Common mode Voltage difference op amp AD629 Datasheet on page 12 says that the use of a large sense resistor skews the output. Why is this so? I can't wrap my mind around any other reason ...
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23 views

Proposal for 5v to 12v dc converter circuit [closed]

Write the proposal for 5v to 12v dc converter circuit
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1answer
48 views

My mobile detector circuit won't work

I'm trying to get C3 to detect RF signals from a mobile phone. Amplify this signal to detect it using an LED. My main issue is simulating the antenna on multisim since multisim doesnt have an antenna!...
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1answer
23 views

Recommendations on pyranometer In-amp design

I'm planning to build a pyranometer amp based on the AD620 In-Amp, at this point I would ask your knowledge on the following details: a) Apart from using a 1.5v dry battery with a (huge?) voltage ...
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1answer
40 views

2-wire analog buffers

How do these 2-wire analog buffers work? The one on the left is driving a current sink and the negative supply is hooked up to the output. The one on the right is a current source driver and the ...
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3answers
117 views

How to get +6V and -6V out of 12V PSU [duplicate]

I am designing a guitar pedal using OpAmps, and i need to feed them with +6V and -6V (beucase the musical signal is senoidal centered in 0V). I need to use a 12V DC PSU for the pedal, and i need to ...
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1answer
51 views

OP amp Comparator not working any tips?

I´m running out of ideas here. I have a device that should always output a 5v signal, with a maximum tolerance of 100 mV (4.95 to 5.05 V). I´m building a "tester" device. My tester will compare the ...
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4answers
104 views

Opamp with multiple feedback loops

I have been trying to figure out how the following circuit works and what it might be good for without any luck so far. What might the transfer function be? Is there a way that analysis can be ...
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1answer
32 views

Looking for a small comparators which do compare a input [closed]

and output when reach the set value。  Or can anyone tell a simple circuit to build one.
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1answer
66 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 ...
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2answers
119 views

Opamp noise: When is a resistor in the signal path?

I am confused as to when a resistor is considered to be in the signal path and when its not when it comes to opamp noise calculations. For instance, take the following circuit: simulate this circuit &...
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1answer
52 views

How do integrator circuits serve as memory devices in continuous time system?

I didn't understand the yellow-marked sentence clearly, and even I did, what does it have to do with the conclusion that follows it? (marked in green). Thanks in advance.. Source: Modern control ...
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1answer
82 views

Opamp 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 0-35V. The accuracy we have decided upon ...
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3answers
94 views

How does an op amp reach equilibrium?

It seems to me that if you try to solve for an Op-amps output (with negative feedback) discretely (i.e. iterating), you never reach equilibrium. Rather, you find the output moves further and further ...
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1answer
66 views

How can I make a circuit that amplifies and mixes, at different ratios, the sound signals coming out of two different instruments

Do I need to use 2 sound sensors to detect the sound signals? If yes, can the sensors be connected directly in the circuit? or do I need to use an Arduino card and program it? Instead of the the ...
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29 views

Input impedance with feedback resistor

One datasheet has the circuit as below. It also gives one term "Input impedance with on-chip feed-back resistor", What is this input impedance.
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3answers
327 views

Opamp + NPN and MOSFET in the feedback network, how to prevent oscillations

Background The task is to add an electronic means to limit the power applied to an electric motor in an industrial setting. The operator normally controls the motor power through a lever that is ...
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3answers
98 views

Asymetrical square wave or rectangle wave amp op

I need to find a circuit that produces a rectangle wave(picture below) and that only uses one capacitor(0.01 micro Farad), 1 amp op with a single supply line(Vsat+ = +10V and Vsat- = 0) and how ever ...
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1answer
29 views

Schematics of PIN Photodiode interfacing with an ADC

This question is in continuation of my previous question. I am moving forward with PCB designing now. I have selected low input-bias current op-amp AD8616 for converting current signal into voltage. ...
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2answers
95 views

Difference between these two op amp circuits

I came across this circuit for a non inverting op amp which is biased Vs/2. I'm wondering what the difference bettween these two circuits are? What is the purpose of R3 in the first circuit and how is ...
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2answers
42 views

cascaded op-amp and critical frequency [closed]

if we have two critical frequency in a cascaded op-amp which one we choose to be the total critical frequency ? i have the critical frequency for the first amp and its gain also to the second amp . ...
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1answer
39 views

Opamp input from transformer

Is it possible to connect the circuit like this. The circuit is from the resolver input circuit, It takes the sine (or cosine) signal from the output of resolver and reduce to appropriate voltage for ...
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2answers
64 views

Controlling an output based on level of AC signal

This is my first post on this StackExchange after years of lurking, so please be gentle! I would like to be able to enable an output (for example an LED) based upon an AC voltage from a split-core ...
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1answer
36 views

How can one of the RC networks of this active high pass filter topology work as an actual high pass filter?

I have seen some previous vague questions related to a similar case but not for this topology. The following circuit (source: http://stompville.co.uk/?p=470) shows an alternative topology for an ...
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0answers
27 views

How To Create Voltage References in Combination Clipper

Context I'm trying to read audio from a headphone jack into a WeMos D1 Mini. I measured the AC voltage of my PC's audio out to be ~800mv when it's at full volume for a 1000Hz sine... but then I also ...
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2answers
40 views

Cannot find the maximum ratings for the output current

For the part of a circuit shown below I'm using an LT1007 but couldn't find any information about the maximum current output can sink or source. They have written every tiny detail but the maximum ...
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2answers
48 views

Why Gain-Bandwidth Product of devices having a simple one-pole frequency response is constant?

I was reading wikipedia page of Gain-Bandwidth Product and got struck at one particular statement. For devices such as operational amplifiers that are designed to have a simple one-pole frequency ...
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0answers
19 views

change in amplified output voltage when high impedance AC source is connected

Is there any change in amplified output voltage when an ideal AC source is replaced by a real high-impedance AC source? Why?
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3answers
48 views

Will voltage gain change in non-inverting op amp when load is connected?

Is there any significant change in amplified output voltage when a load is connected to the output compared to a no-load connection in a non-inverting op-amp? Why?
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75 views

Extending the negative rail range for an Op Amp

I'm building a Transimpedance amplifier using the ADA4530-1 op amp by Analog Devices. I'm attempting to sense a fA current signal that is always negative and I would like to see if it would be ...
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1answer
26 views

Virtual SPDT with half-bridge and op-amp comparator

I have the following circuit composed of an op-amp comparator and a mosfet half-bridge: I would like to "confirm" the following: if VBUS is floating, nothing will happen. Especially, there will be ...