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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CMRR test methodology and effect of open loop gain

I am trying to test the CMRR of opamp and so measuring offset variation across Common mode range in unity gain mode. I have gone through many articles on CMRR measurement. All those are suggesting a ...
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41 views

How to Run 12v 1A Electromagnet From Arduino (3v) Without External Power Supply

I have a project that I am working on that uses a micro controller to control an electromagnet that I want to run with a 3.7 volt battery. I would like to reverse the polarization on the electromagnet ...
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45 views

Cell phone detector circuit design

This circuit I found on the internet detects mobile frequencies that transmit to the base station in the range of (0.9 to 3 GHZ). I want to understand how can I get or calculate the values of some ...
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43 views

regulator ac to dc with

I am studying for my EE exam ,I understand the general working of the circuit but there is some details about it I have to know. this regulator supply 24 volt with puissance nominale 200watt. it ...
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1answer
45 views

Adding two signals and finding the RMS and Peak to peak value of the output signal

I would like to start by saying I have been solving exercise related to Op amps and how to find RMS values and Peak to peak values. But I got stuck on this exercise. Basically, two signals has to be ...
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59 views

DC 0-1V to 0-10V voltage amplifier

I have an Horiba gas analyzer having the analog out linear 0-1. My data logger (10 bit) has the input 0-10V. Of course, I can use like that but on higher ranges for analyzer gases the reading after ...
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2answers
50 views

dual input temperature comparison circuit

I would like to build a comparator circuit that will compare two varying temperatures and operate a relay to a fan when one is greater than the other, but release the relay if the opposite is true. I ...
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21 views

Protect 6S lipo from deep discharging

is it possible to prevent a 6S lipo (typ. 22.2V - 25.2V) from over discharging, using a simple Mosfet? The goal is to cut-off the battery if the voltage falls below 18V. Furthermore, it would be ...
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1answer
70 views

Op-amp saturation problem

My design: Two cascade connected inverting amplifiers. My problem: The output of second amplifier is saturated from -0.6 to -0.7V. The supply of OPAMPs is dual(+5-5V). What is the problem? How ...
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63 views

How to generate Duty Cycle from DC without 555

I am currently working on a simple circuit which includes creating duty cycle from DC. Also, I need to change it's pulse width with time. I have decided to use op-amp relaxation oscillator to produce ...
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439 views

transistor level design of Op-amps

How do we realize the design of a simple Op-amp with Bipolar Junction Transistors or MOS Field Effect Transistors alone? I mean I understand the need for differential amplifiers for providing a ...
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1answer
57 views

Final voltage of two parallel (switched) capacitors

I am trying to obtain a resistance-circuit equivalent to a switched-capacitor circuit. It is the first stage of a ladder filter. simulate this circuit – Schematic created using CircuitLab ...
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27 views

How to design mobile charger using lm3622

I want to design mobile charger using LM3622 Lithium-Ion Battery Charger Controller. I read datasheet by TI( http://www.ti.com/lit/gpn/lm3622 ) , but much of its content I can't understood. So please ...
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1answer
33 views

Do my specific constraints prevent me from using this Zero and Span Amplifier?

I am interfacing a thermistor with an ADC, and I have found a circuit that, at first glance, appears to suit my needs. A zero and span circuit using a single op amp. ...
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2answers
88 views

Suggestions to interface a photodiode in the MHz range

The task at hand is to read the variations of incoming light at speeds up to 1 MHz, with some dynamic range capability (10-1000lx with 1% accuracy would suffice). This is to be used in a device which ...
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2answers
50 views

LM358 Single Supply problem

I am trying to build a low pass filter circuit from the LM358 datasheet from TI. Looking at the pinout and building the circuit I cannot get something basic like this filter to work. I have everything ...
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2answers
86 views

Assumptions for an op-amp and when they do and don't hold?

Correct me if I am wrong but the following is what I think the assumptions we make for an ideal op-amp: Negative feedback (output connected to the inverting input): No current goes into either of ...
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31 views

3rd harmonic filter circuit to analyse leakage current

Anyone help me to design 3rd harmonic filter circuit using op-amp. Input voltage is 45V, 60Hz. The output should be in current 180Hz.
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116 views

Op Amp's Negative Power Supply to Ground

I am using a standard 741 Op Amp from TI. For me to amplify any signal, I am required to set +Vs = 15 Volts and -Vs = -15 Volts. I am now concerned as to what will happen if I connect -Vs to 0 ...
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1answer
41 views

Cascaded vs. non-cascaded bridge-tied load circuits using opamps

A bridge-tied load (BTL) amplifier circuit doubles the output voltage (and potentially quadruples the power, output current limits notwithstanding) by using one "master" opamp for gain followed by ...
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2answers
40 views

Oscillating active filter

I built an 2nd order active highpass filter with cut-off frequency at 800Hz using an OPA847 (and R18=39.2k, R19=16.9k, R16=11.3k, R17=11.3k, C7=20nF, C8=20nF). Simulation works fine. In real life ...
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1answer
161 views

Why is my op-amp chopping up my signal?

I have built an instrumentation amplifier out of two op-amps in a quad op amp (MCP6L04T). The input signal is coming from a low-impedanece source (~17k) and most of the information in that signal is ...
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115 views

Operational amplifier used as a current source

As a laboratory task at my practical engineering school we were asked to make the simple circuit shown below, prove that it acts as a constant current source regardless of its load, and answer some ...
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53 views

LMH6611 (OpAmp) draws too much current

We are using the LMH6611 OpAmp from TI as it offers high current rail-to-rail output (100mA) and high frequency (345MHz), which seems to be quite unique in this combination. In addition, the power ...
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101 views

Opamp Misbehaving in Constant Current Source Circuit

I'm planning to build a current regulator for a power supply and I'm prototyping a number of different regulator circuits. First up, the op amp and transistor circuit shown below. I felt I ...
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30 views

Thevenin equivalent of the input of an op amp?

In the image above, the subcircuit in the box in the top circuit is reduced to the subcircuit in the light box below it using Thevenin's Theorem. I don't really see how to get a Thevenin equivalent ...
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117 views

Why this current regulator won't regulates?

I'm trying to make a current regulator to power up some LEDs. For now I'm working only on PSpice models. The circuit above works well if the sensing opamp is configured as voltage follower or even ...
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2answers
50 views

MCP602 alternative?

What can I substitute in place of the MCP602 in the following circuit? It is a pulse rate detector.MCP601/2/3/4 are not available where I live. I have attached the relevant instructable and the MCP602 ...
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62 views

Measure capacitance with OPA604 and this circuit

I am following this circuit: to measure the capacitance. The opamp is OPA604 with supply voltage +-5V, Cx and Cf is 5pF, Rf is 10Mohm, the diode is 1N4007 and the output capacitor is 1nF. I also ...
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39 views

Generating a high speed single-ended voltage output from differential currents

I'm working on a signal generator using a high speed DAC, which has balanced current outputs (two outputs, each 0-20mA, 180 degrees out of phase). The DAC is 250MSPS, so I'd like the analog frontend ...
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53 views

Why does a Schmitt trigger work in saturation region?

Given this circuit simulate this circuit – Schematic created using CircuitLab I am trying to prove that the opamp works in saturation region as instructed in the first answer to this ...
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1answer
71 views

Over driving opamp inputs

First the background. I’ve got a customer who wants to drive the inputs of an instrument from a separate signal generator. One of the inputs I designed correctly (series resistor and diodes to the ...
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60 views

Opamp buffer for ADC - single ended signal conditioning

I have a problem with my simulated signal conditioner on Multisim. Input signal 11-13V @ 10KHz MCU ADC input is max 0-3.3V The output of the opamp (B) is slewed compared to the input (A). I have ...
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74 views

OpAmp: Better to actively attenuate, or drive full range into a divider?

I want to get a +-15V differential signal (60Vp-p) into an ADC that has a single 3.3V supply. When I asked a friend to proofread it, he was concerned about the noise performance of R5-R6 vs. using ...
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91 views

How do operational amplifiers work, exactly?

Can you offer a website or pdf where I can understand how we can calculate current, voltage,etc. in an operational amplifier and how it works exactly (the direction of the current, feedback,etc. )?
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29 views

opamp input protection for piezo as microphone

I have a Piezo buzzer that I made into a contact mic, across a 1Meg resistor. That goes into an opamp that I use as a differential pre-amp. I'm thinking I should add some diodes to protect the ...
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3answers
139 views

Why Op amp amplifier's voltage difference zero ? [duplicate]

when I'm studying Op-amp amplifier , in the derivations we always take voltage difference between inverting input and non inverting input is approximately zero . But I can'f find any explanation "why" ...
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52 views

instrumentation of V-divider dual-thermistor circuit

here's the circuit - voltage divider with 2 matched thermistors ("matched" means close enough that the measured temperatures when thermistors are right next to each other comes close enough for my ...
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2answers
77 views

Transfer Function of PI Controller

Circuit below is an op-amp summer combined with PI controller. simulate this circuit – Schematic created using CircuitLab What is transfer function of this circut? How to calculate each ...
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76 views

Calculate Vout from an op amp

I have a op amplifier for which I want to calculate Vout depending on Vin. The circuit looks like this: I know that with a circuit that just has ground connected to + of the amp, i can just ...
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147 views

Questions on Operational Amplifiers

What I've learned so far from Navy school is that operational amplifiers are used as a substitute for transistor amplifiers and they contain three main circuits: the differential amplifier, common ...
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62 views

What type of op amp should I use in this thermistor signal conditioner?

I'm designing a thermistor signal conditioner for existing probes. I'm not linearizing in hardware, there is plenty of time to do it in firmware. The thermistor has a resistance of \$\text 7.5\text ...
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2answers
48 views

Can this gyrator handle high current and/or high voltage?

Since I first got introduce to the Antoniou Inductor while in university, I've always been amazed at it. I've never built or used one, but I am thinking about using it to simulate an inductor for a ...
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29 views

Protecting opamps from back-EMF, necessary or common in 70/100V audio?

Clayton and Winder's opamp book 5th ed. p. 283 briefly discusses the use of Zener diodes to clamp (as a TVS) voltage spikes from inductive loads from taking the opamp's output stage above its power ...
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74 views

Basic Filter Design

Need help with basic filter design. Firstly there is a low-pass filter(pictured below). I am supposed to derive an expression for the amplitude of the output voltage as a function of \$R_1\$, ...
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1answer
64 views

Op-Amp difference amplifier low-pass filter

I have the following (summing, single supply) difference amplifier circuit: How can I extend this circuit to a 1st or 2nd order low pass filter, with a corner frequency at about 20kHz.
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44 views

Why is a 0V DC point at the output of an op amp critical for feedback?

I am designing an op amp that consists of an active loaded single ended output differential amplifier that is connected to a buffer stage and then an output stage. When the input signal is connected ...
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25 views

Understanding Block Diagram for Load Switch

I'm looking at the Vishay SiP32431 and am confused by the block diagram, copied below. I understand the P-Channel at the top, but what are the triangles? What is the difference in level-shifting ...
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37 views

Help with Op-Amp project

I have an Op-Amp project, and im stuck on the last part of it; I was wondering if anyone would be able to help; http://imgur.com/GdEWKMN (project outline) http://imgur.com/FVPEr4C (Part A solution) ...
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42 views

Opamp filter cutoff frequency not as expected at higher frequencies

I'm still working on learning Butterworth filters. So far this weekend I went back to school, read about Lapace transforms, poles and zeros, Saleen key design, and finally back to Butterworth filters ...