DC Instrumentation Amplifier Circuit

Posted on Feb 7, 2014

A common challenge for experimenters is increasing the gain of a low level DC voltage for recording or analysis. Most instrumentation circuits require building a complicated project with dual power supplies and high accuracy components. A simple solution is to use an Integrated Circuit (IC) specifically designed for the purpose, such as the INA122. This particular instrumentation amplifier IC is very easy to use because it operates from a single supply voltage and only one external resistor is needed to set the DC gain. Here is the circuit diagram showing how to use the INA122 to make a basic DC amplifier.

DC Instrumentation Amplifier Circuit
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In this particular example the gain is set to 205X. The gain is calculated according to the formula Gain = 5 + (200K / R). The maximum output signal from the amplifier cannot exceed the supply voltage. The meter or device which reads the output from the amplifier should have a high input impedance. This same circuit can be used to amplify a differential voltage by connecting Pin 2 (V- in) to the reference voltage instead of ground. There are many more examples for using this amplifier.

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