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How to Measure AC Milli-volts Using IC 741

Last Updated on July 15, 2019 by Swagatam 2 Comments

caution electricity can be dangerous

In this article we study an op amp based circuit designed to measure AC millivolts accurately, let's learn the details from the following explanation.

The circuit shown below can be used to measure DC potentials in the range of milli-volts. The circuit is highly sensitive and is calibrated to measure voltages in the range of  1 mV minimum to 1 V maximum.
Measuring potentials in the order of milli-volts is generally difficult using ordinary multimeters. The circuit shown here can be used for sensing minute AC signals in the range of as low as 0.1 mV.

Circuit Operation

The transistors Q1 and Q2 has been configured as high gain feedback kind of amplifier, with the shown components the amplifier stage has been foxed to produce a gain of 100.
The next stage which consists of  two 741 ICs, IC1 and IC2, have been wired up as precision rectifiers.These together are able to generate a gain of 10 over bandwidth that might extend above 50kHz or below 20 Hz.
The over all gain of the circuit therefore falls in the range of 1000, which makes it imperative to have signals below 1mV well attenuated.
The setting of the circuit does not involve much of complication, just the preset RV1 needs to be adjusted initially for making the connected meter show a zero when there' no signal at the input.
All resistors marked with asterisk must be 1% rated, MFR types.

Measure AC Milli-volts circuit

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About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

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Comments

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  1. Prawin says

    April 27, 2021

    PLS BC547 BD139 USE 10 WATT FM
    TRANSMITTER CIRCUIT…(USE HI VOLTAGE) OR OUT BUT STAGE 2N2222
    PARALLEL CIRCUIT..PLS

    Reply
    • Swagatam says

      April 27, 2021

      sorry don’t have that circuit right now with me….

      Reply

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