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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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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35 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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71 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
50 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
46 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
79 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 ...
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63 views

Repeating/Cascading Op Amps

I have the front end of a photodiode detector. What is the point of the 3rd Op Amp? The output from U2C gets divided in half from R14 and R18, then it just gets double by U2D again. Is there a reason ...
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195 views

If op-amp offset trims are provided, but not needed, what is the best practise for connecting them?

I'm using op-amps with offset trims available, but not needed as they already have very low offset voltage. What is the best practise for the PCB pad connections - should they simply be left floating? ...
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94 views

Operational Amplifier frequency problem

I am using an operational amplifier in an inverting configuration with a gain of 10. (-R2/R1= 10), with a high cut-off frequency of almost 30 Mhz. However, while testing whenever I apply an input ...
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1answer
45 views

Are these two OP-AMP circuits behaving different?

I am looking for DC biasing circuit for a bipolar square wave with frequency < 10 MHz. I'd like to make a square wave with high 1.5-1.7 V and low (-1.5)-(-1.7) V into a square wave with high ~ 5 V ...
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40 views

Schmitt trigger design to control lead acid battery charger

I've found a very good explanation on schmitt trigger circuit design here -What is a Schmitt Trigger and its application exactly? But the design is done considering same reference voltage and the ...
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1answer
47 views

Common-Drain Amplifer vs OP-Amp for unity gain (voltage Follower)

What is the difference between using a nFET vs OP-Amp as a unity gain amplifier, i.e. voltage follower. Application: Provide constant voltage with a variable load, see example below: Min Current ...
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53 views

How to determine current limiting resistor values for push pull amplifier driven by op amp?

I'm looking to increase the output current drive of a high voltage op amp using a push pull amplifier. The OPA454 datasheet includes an application circuit to do exactly this, and includes some ...
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1answer
55 views

Converting a 4 to 20 mA signal to 0 to 5V

I am trying to convert a 4 to 20 mA signal to 0 to 5V. Till now I just used a 250 Ohm resistor to convert my signal to 1V to 5V. Now I am trying to increase the resolution by adding a OpAmp. When ...
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45 views

node voltage conflict

background: My goal is to use an Arduino with two proximity probe (sensors) to achieve some output. It is worth mentioning that the output of the proximity probe has two components: DC output that ...
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1answer
135 views

Why use a transistor for getting a Constant Current Source in a circuit with an op amp?

I have used the above simple circuit for a constant source where \$V_{\text{in}} = -5\$V, \$R_{\text{in}} = 390\Omega\$, \$R_f\$ is the load which ranges from \$110\$ to \$170\Omega\$....would using ...
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1answer
84 views

Signal on top of PWR line

See edits at bottom: I'm trying to design a network of circuits (see example below), in which a modular circuit (non-static, can be change, with high variability in current draw) is connected on any ...
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2answers
65 views

Input impedance of a non-inverting op-amp

From what I've read (and simulated), the feedback loop of an op-amp modifies the input impedance of the non-inverting input. The value specified in the datasheet is the open-loop input impedance, and ...
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1answer
78 views

How to power off a dual supply op amp?

What is the best way to power off a dual supply op amp (LM741)? Should I cut the positive, negative, or both? Thanks! I’m building an audio oscillator using four op amps, and I’d like to be able to ...
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3answers
119 views

Why doesn't LTSpice predict this op-amp oscillation?

I'm developing a circuit to act as an electronic load for bench testing power supplies. An earlier question about how to test this circuit received several very useful answers and can be found here: ...
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1answer
31 views

Low current more susceptible to noise?

Supose I have an opamp with pnp input stage (constant current flowing out the input pin), like the following: simulate this circuit – Schematic created using CircuitLab Would the input ...
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2answers
81 views

Input range of operation amplifier

Lets have a look at the following circuit: (Input waveform is sinusoidal and Vpp would be ~32V) The input waveform should represent an AC Source from a ...
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1answer
121 views

What should I do with the unused Op-amp inputs?

I am building a simple inverting operational amplifier circuit where I am using a chip with dual amplifier. I am only using one of the two amplifiers. What should I do to the unused amplifier's input ...
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2answers
41 views

What is the effect of current noise in this op amp circuit?

I have modeled a non-ideal op amp as an ideal op amp with a noise current I_n flowing between its inputs: In this circuit, I have also modeled a non-ideal voltage source as an ideal voltage source ...
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1answer
35 views

Differences between preamplifier, instrumentation amplifier and LNA

I am confused about the definitions of these amplifiers. It seems LNA is used for RF frequency band but I also see people using INA's for receiver. Why LNA's need careful impedance matching but INAs ...
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1answer
78 views

Circuit help. I want a Voltage gain from 5 volts to 10 volts.

I need some circuit help.. I am trying to boost my voltage from a 5v source to a 10v output so I want a Gain of 2. I Ran the simulation and built the circuit exactly how it is shown in the figure ...
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2answers
29 views

Why am I getting an error in my transfer function?

I'm trying to solve part b here, and my transfer function is coming out as -1.25s/(s^2 + 2.05s + 1 instead of the given -1.25s/(s^2 + 1.6s + 1). Since there were no initial conditions, I just ...
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1answer
38 views

loading on rail voltages in OPAMP

if an opamp is having +15/-15V rail to rail voltage, is there a way to determine how much will either of these power supply get loaded? will they get loaded equally? what happens if I use +18, -12V ...
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2answers
79 views

General rule for current flow in op amps?

I'm a first year student doing elec eng. and I'm wondering about the direction of current in an op amp (Where the current flows from to where it is going). I'm wondering this so I can use KCL to find ...
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1answer
36 views

Using a low voltage opamp for feedback with high voltage mosfet?

I've been looking at Piezo drivers lately. They are effectively 0->100v output amplifiers with 0->10v input. Which can source ~60mA, at a few KHz. The drivers I've seen mostly use high voltage opamps ...
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3answers
99 views

How to test op amp stability?

I've got a circuit I'm developing using an op amp to drive a power MOSFET for an electronic load: I'd like to test it for stability, but I don't have enough experience to know what perturbations ...
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66 views

0-1 V input to 0-5 V Output [migrated]

We have an instrument that has analog output of 0-1 volts and we need to convert this to 0-5 volts. What is the best op amp to use for this and how should the resistors be set up? Any help would be ...
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1answer
40 views

Calculating gate resistor value for enhanced active-region stability

I'm working on an electronic load design driving an n-channel MOSFET with an op-amp. I'd like to consider adding a gate resistor (R3 in the schematic) to improve the stability. I've searched quite ...
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1answer
80 views

Is it ever useful to add a capacitor between op amp inputs?

Is it ever a good idea to add a capacitor between the inputs of an op amp? I'm building an electronic load roughly inspired by some of the Dave Jones derivative circuits out there. I've adopted the ...
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1answer
44 views

Solving Schmitt trigger circuit using the superposition theorem

In order to solve a Schmitt trigger circuit implemented with an op-amp (or a comparator) connected in positive feedback, this wikipedia page uses the superposition theorem. My question is : why can ...
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1answer
83 views

How do I amplify an input signal to match the peak of another signal

I would like to build building a Voltage Controlled Oscillator (VCO) for audio applications beginning with a relaxation oscillator build from op amps. Adding a potentiometer to the feedback loop ...
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4answers
401 views

LM324 for 10,000x gain?

I'm looking to use the LM324n (http://www.ti.com/lit/ds/symlink/lm124-n.pdf) single-supply op-amp in non-inverting mode: The goal is to take a voltage of around 100uV and multiply it to around 1V ...
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2answers
121 views

Amplifying a high frequency signal of 30 Mhz or above using OpAmps

I am testing a 34 Mhz amplifier in an inverting configuration with a gain of 20. The cutt-off freqeuncy of amplification stops almost at 15 Mhz , which is very low. I want it to continue up to 27 ...
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1answer
87 views

LM324 Difference / Instrmentation Amp 1mV Signals

I need to amplify 1mV signal from a wheatstone bridge (no DS available). 5kg max weight; output is 1mV/Kg @ 5V. The resistances are 880+880 and 749+749. Currently I only have LM324 and LM358. And ...
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338 views

The Op-Amps don't work correctly for this circuit [Thermocouple]

I'm trying to connect a thermocouple to an Op-Amp to amplify the output of a thermocouple. this is the circuit: Also for R17 I put a 5k09 resistor instead of 6k8 and for R18, 1k032 and for R19, ...
2
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1answer
71 views

Arduino Uno - Analogue Signal Conversion Issues

The output of my Low Noise amplifier is a rough sinewave with a peak-to-peak of 1.7V and is shown in the oscilloscope trace below. I would like to use one of the analog pins on the Uno to perform ...
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1answer
200 views

What does this schematic of an Op-Amp and Capacitor mean?

I'm still learning about electronics and electricity. But I'm puzzled by this question from a past exam. I'm not sure if any voltage is getting across the capacitor, since Vin and 3v are seperated ...
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2answers
99 views

How to set up load sensor in a full bridge with amplifier?

I I'm somewhat new to electronics so forgive me for what I don't know. I'm learning as I go along here. The overall project is I'm trying to make a scale connected to an arduino board that will ...
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2answers
68 views

voltage current converter by op amp circuit

I am trying to convert 5V to a constant current source for op amp I use AD822. for 250 ohm I use 180 ohm, so I should get a current of 28 mA. I verified when Rload = 0, 28 mA across negative ...
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2answers
56 views

Opamp constant on

I have a weak signal (from a photo-diode) which I need to amplify to drive an LED. I try to accomplish this with an OpAmp TL081 and the circuit given in the image. What the circuit does: When there ...
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Adjusting ground level to 1.5 volts for LM386 audio amplifier

I am attemting to use an STM32F4 Discovery to play music through LM386 amplifier. I have tested the LM386 circuit with a spliced headphone and mp3 as input and now attempting to play the music off one ...
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29 views

transfer function for operational amplifier [duplicate]

I need to clarify whether the transfer function derived is correct for the attached circuit: $$\frac{E_o}{E_i} = \frac{R_2 -(1/Cs)}{R_2 +(1/Cs)}$$
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1answer
50 views

What to do with the Balance and NC pins?

For a course project, we are to use an LF356 operational amplifier What does the Balance and NC do? and I do not think I need it for my project(Sallen-kay filter 4-pole). Do I just ground it?
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1answer
82 views

Diode and Op Amp

Can you help me finding the expression of Vo(Vi) and graphing Vo(t)? I have simulated it in multisim but i can not understand when the diode passes current or not.
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3answers
46 views

Non Inverting Summing Amplifier - Ripple Gain

I've created the following non-inverting summing amp. This seems to sum flat DC fine although if I add ripple, the ripple get amplified, surely this should only add the ripple. Why is the ripple ...