In-Amp Common-Mode Range / Gain Calculator

This tool calculate the common mode gain for instrumentation amplifiers using gain, differential voltage, and various other input parameters. It calculates both the internal node voltages and the output voltage of the part. It also calculates the resistor needed for a particular gain or the resulting gain using a certain resistor.

Instructions | Troubleshooting | Related Information

Positive Supply  

Equivalent circuit

Differential Voltage

Common Mode Voltage

K ohms
Reference Voltage

Negative Supply  

Equivalent circuit shown


Enter data in the fields provided. If an input is out of range an alert will appear.

Click "Update" or tab to another field to see node voltages annotate the schematic on the right. Internal node voltages are for the equivalent 3-opamp circuit, assuming a 0.5V level shift. This may not reflect the actual internal implementation.

If the combination of inputs causes internal or external limits to be exceeded, the problem node value will be highlighted in red and an "Out of Range!" message will appear. When this message is present, all node values should be considered invalid.

Only one of "Gain" or "RG" can be specified - the other is computed automatically.


No special issues are known to exist with this calculator at this time.

The latest version of the Java Applet Plugin is required to run this design tool. It can be downloaded here.
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Related Information

A Practical Review of Common Mode and Instrumentation Amplifiers (pdf, 57,234 bytes)