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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Ultra low noise microphone preamp, using LT1115, pesky bias ground path

I was trying to build a simple ultra low noise preamp or pre-pre amp for a ribbon microphone. The Ribbon microphone itself is a couple hundred mOhm with a 1:37 step up transformer. They like to have a ...
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27 views

one-sided saturation with op-amp and RC high pass filter

I am working with a photodetecting circuit built as follow: When I drive an LED ON and OFF, I get the following waveforms: Blue indicates that the LED is turned on when a voltage is high and ...
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2answers
84 views

what are the possibilities for Op amp's power supplies?

I am looking for a way to remap a voltage between 0..24 volts to 0..5 volts in order to read this voltage in a microcontroller ADC.For that ,I am intending to use an operational amplifier as an ...
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2answers
47 views

What can be inferred from the frequency an op-amp is oscillating at?

For whatever reason, I seem to create a lot of oscillators in the course of developing circuits involving op-amps. I'm wondering if the frequency of oscillation, which normally appears to be quite ...
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2answers
52 views

Positive feedback and virtual short

Can anyone please explain with sufficient mathematics,that why virtual short concept is not applicable to an opamp in positive feedback.
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40 views

How to remove noise from the output of inverter circuit created from 741 IC [on hold]

I'm trying to provide a negative input to ADC0804 through an inverter circuit. The inverter circuit is made using IC 741. But, the inverter circuit is giving a lot of noise. Is there any way to ...
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1answer
48 views

practical concideration for op-amp differential amplifier

i'm trying to make a current sensor based on an op-amp differential amplifier with a unity gain (all resistors are equal so to have the best CMRR.) The output of the op-amp differential amplifier ...
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1answer
24 views

Feedback Gain Loss of Transimpedance Amplifier

I have designed a single-supply (3.3V) potentiostat that initiates electrochemical reactions, converts the generated electrochemical current into a voltage via a transimpedance amplifier (op-amp used ...
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29 views

Is it okay to replace voltage feedback op-amp with current feedback op-amp?

I have an LED driving circuit and a photodetecting circuit drawn as below: LED driver Photo detector TL972IP has GBWP of 12 MHz. But my application requires a very high bandwidth up to 30-60 ...
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1answer
141 views

Impedance seen by the inverting terminal

Actually it is given in Sedra smith that to reduce input offset current effect is to use a resistance at non-inverting terminal of the opamp whose value is same as the DC resistance seen by the ...
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1answer
66 views

Inverting Opamp Simulation

Calculation show Vin should be 1.02V as no current will be drawn towards negative terminal of opamp and Vout should be -1.02V. But simulation show Vin to be 114mV and Vout to be -114mV. There must ...
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32 views

Trouble splitting off LFO signal to drive LED

Background: I am trying to build a very simple noise box that doesn't need to be tuned to 1V/Oct or anything special. It simply has one VCO, two LFOs, and a VCA. The circuit is powered off of a dual ...
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30 views

Analysis for unclear circuit(Differential, Integrator, Comparator…etc)

I am developing an embedded system using MCU that outputs signals and voltages to an uncertain circuit that is connected with batteries for charging/discharging. The only paper schematic was given to ...
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2answers
52 views

Understanding electrical characteristics of comparators: input offset voltage and open collector output

I have two questions regarding the electrical characteristics of comparators: Is there a way to adjust the input offset voltage of a comparator to fit a custom application? Which comparator ...
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0answers
37 views

Tips for improving this PT100 sensor amplifier circuit?

I'm designing a circuit to read a PT100 temperature sensor using an OP-amp and the ADC of a PIC 16F1788. I've designed the following circuit: The PT100 sensor is labelled PT100. The basic idea is a ...
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1answer
38 views

What is the use of dual input, unbalanced output differential amplifier in an operational amplifier?

Why do we use an unbalanced output Differential amplifier and not a Balanced one?
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38 views

VCTCXO control voltage circuit recommendations?

I'm building a frequency calibration rig. Right now, I've got a fixed TCXO and it has an uncalibrated drift versus GPS of around 0.185 ppm ±50 ppb. I'm prepared to simply subtract 0.2 ppm from the ...
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4answers
47 views

TL084CN Unexpected Output

Want to get binary Pin 7 output (0V or 3.3V), dependent on light intensity on the photoresistor. But the output is not as expected. I have built the circuit below with the help of LF33ABV 3.3V ...
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5answers
4k views

Is it safe to connect an Arduino to the human body?

I want to create some project which uses an Arduino to collect and display ECG data. It uses two electrodes which are attached to the body (on the chest). The signal is then transmitted through ...
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1answer
73 views

Attenuation of Input Signal

Schematic Simulation Model The circuit is simple , it includes a 3mA Sine Current source in parallel to a Resistor that converts it to voltage and supplies it to the differential amplifier with ...
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4answers
276 views

Op Amps: how do they know whether the supply is split?

Most op amps can operate in single and split supply configurations. However, I cannot see how this is possible. If I connect voltages \$V_\text{SY}^+\$ and \$V_\text{SY}^-\$ to the positive and ...
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2answers
292 views

Why is an op-amp necessary for photo detecting circuit generally?

I am trying to build a photodetecting circuit with a photodiode Hamamatsu Si PIN photodiode S6036 As I don't have much knowledge about circuit, I think a reverse voltage supply and a resistor are ...
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1answer
26 views

DIY Spectrometer/Colourimeter 430nm and Log Amps, Are all log amps equal in this case?

received some good help in the past on another project (vacuum pump). I'm now moving on to my current project, to build a colourimeter or 430nm spectrometer for measuring the colour of beer. This ...
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40 views

A: Why does the sound that out after LPF become smaller

I'm trying to make circuit to record and analyze heartbeat sound in my phone through 3.5mm jack. I build the preamp with LM358 like this It works I can hear my heart beat sound, but alot of noise. I ...
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1answer
32 views

Adjusting output bias of op amp is different with what I calculated and expected

Yesterday, I've posted attenuated and biased output from op-amp And attenuation has been solved and bias remains. After googling and with answers in stackexchange, I've built and improved the ...
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60 views

How to build a DC amplifier using opa552

I am working on a project which requires me to amplify a dc supply volatge of 2v to 20v. I used the opa552 op amp with an input resistance of 100 ohms and a feedback resistance of 1k ohm (i.e., Rf/Rin ...
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2answers
149 views

attenuated and biased output from op-amp

I've been struggling on build a noninverting amplifier with TL972IP (datasheet). Here's what I've made: Orange is for VCC+, Yellow is for VCC-, Green is for GND. Blue is for a signal input. ...
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39 views

Differential input voltage of op-amp with feedback

I learned that either positive or negative feedback on an op-amp makes voltages at a noninverting input and an inverting input same. Then, I think I don't need to care about absolute maximum value ...
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1answer
35 views

How would adjusting the bias on an op amp effect the signal?

I am using an op amp to boost an audio signal. The bias, it appears, is typically half of the input voltage. What kind of effect would it create if the bias was to be adjusted up or down? Would ...
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35 views

How to prevent or slow down the discharging rate of capacitor once it has detected the peak values?

I have load cell-sensor that has a sensitivity of 2mV/V. I am using an instrumentation amplifier to amplify the sensor output depending on the load or force applied on the sensor. Followed by the ...
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2answers
105 views

Calculate voltage and current in an op amp

Hi I have a op amp circuit that i need help in calculating some values (see image, Å=A in further description) The values i have are: ...
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2answers
57 views

Voltage drops when a signal is fed into op-amp comparator

I have a function generator SFG-2110 from GW Instek. I set it to generate a square wave with max/min of aroudn +- 1 V. And I checked with an oscilloscope. However, when I connected outputs of the ...
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364 views

Gain of filter is higher than calculated - why?

I have this circuit: simulate this circuit – Schematic created using CircuitLab The op-amp is being run off 15 and -15V supply rails, and I am using a signal generator to input a sine ...
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84 views

Ghost charge in op-amp circuit

I have a Trans-impedance amplifier which is made of 2 stages. The first stage converts the current into voltage using 12 Mega-ohm resistance with 47 pf capacitor in parallel. The second stage ...
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1answer
38 views

Photoamplifier circuit analysis

I am trying to analyze the following circuit, in which a photodiode has been replaced by its equivalent circuit: The circuit has already been analyzed in the document from which I have obtained the ...
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1answer
64 views

Circuit to solve algebra problem?

I am trying to get the hang of op amps and have a few questions about circuits that solve algebra problems. I would like to solve two problems where \$X\$ is an input voltage and \$Y\$ is an output ...
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2answers
225 views

Why is input offset voltage so bad? (op amps)

Take a typical application of an op amp - a photo amplifier: In the circuit above, since input offset voltage is a dc characteristic, it is modeled as a dc source near the inverting pin of the op ...
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1answer
60 views

Output from amplifier is clipping

I have the following circuit and I want to process the output of the op-amp through an ADC. However, as you can see in the picture the signal is clipping at 1.89 Volts, rather than 3Volts. Why is it ...
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3answers
53 views

Calculating Fc (cutoff) of series to RC to ground on inverting input of non-inverting amplifier

Regarding the chosen answer for: How does this OP-AMP non-inverting amplifier work? The following circuit is given, and it says that $$F_c = \frac{1}{2\pi R_1C_1}$$ simulate this circuit ...
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1answer
136 views

Terminating unused unity-gain Unstable op-amp

I am trying to terminate the unused unity-gain unstable op-amp. I have tried to terminate it with the typical unity-gain stable configuration ...
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3answers
128 views

Using wxMaxima to obtain a transfer function from T-twin filter & op amp

I'm trying to get the transfer function from this circuit using wxMaxima So first using the ideal op amp model I know Vx = Vy and I can know Vy from that voltage divider from Vo Now I solve this ...
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1answer
109 views

Make an opamp go rail-to-rail on a voltage higher than opamp supply

So I've chosen to work with an High Frequency Opamp that can only use 5V for power (I can't use any other Opamp). But I need the signals to go Rail-to-rail at say, 24V. So naturally I thought I'd just ...
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1answer
43 views

How Much Current Draw From Speakers/Amplifier?

So I plan on using the VS1053 Codec connected to a class D Amp (2 x 2.8W channel) with two 3W 4 Ohm speakers. If I supply 5V to this setup, what would the current draw be at full use? Codec: ...
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3answers
165 views

Op-Amp + MOSFET = Constant Current Power Source (?)

I'm trying to make my first circuit from Horowitz and Hill- a constant current source that sits above the load, and can (hopefully) source 1A. I decided to use the components I had on hand- an ...
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4answers
190 views

Is it voltage or power of the signal amplified when the opamp amplification is given in dB unit?

Today, one of my colleague said that he entered a preliminary examination in a company after his job application. One of the questions is exactly "Design a non-inverting amplifier with 20dB gain.". ...
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1answer
40 views

OP AMP fabrication technologies impacts on design

I am referring OP AMP selection guide for implementing it in medical application where it involves optical sensing using photo diode then I/V converter and ADC for data conversion. My question is how ...
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3answers
97 views

This op-amp configuration is giving me trouble

I came across this configuration earlier today and can't for the life of me figure out the equation for Vout: It looks like a unity-gain differential amplifier but the ground resistor on V2 is ...
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2answers
75 views

photodiode amplifier

I am a mechanical engineering student and I am working on a research project where we want to use a reverse biased segmented photodiode (OSI SPOT2DMI series) to detect deflections from a high speed ...
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1answer
51 views

op amp rails and it's inputs

I am trying to feed this voltage measured by the oscilloscope to a voltage comparator. by design the voltage should swing between +0.7 and -0.7 . BUT since the voltage is not referenced to ground i ...
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1answer
86 views

What do we need the op amp for in this current-to-voltage converter?

I'm still very new to electrical engineering and at the moment trying to get my head around the concept of the ideal op amp. In Fundamentals of Electric Circuits by Alexander and Sadiku the following ...