μblog: engineering from the trenches

When dealing with two op-amp instrumentation amplifiers that have a small footprint, we are often faced with a non-unity minimal gain value. The minimum gain is 5 for the ina2332 for example. The reasoning behind this can be found in chapter two of the Analog Devices’ Op Amp Application Handbook. (Not to be confused with Texas Instrument’s Handbook of Operational Amplifier Applications.) By increasing the gain we increase the allowable common mode input range as well as improving the amplifier frequency response. Everything has its limits, so be mindful that the CMRR of the two op-amp instrumentation amplifier suffers at high frequency due to slight phase shift between the signal that goes through the first amp and the signal coming into the second amp.

( sboa092a.pdf ) ( Op_Amp_Applications.zip )

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