By their very nature, in amps are a good choice to condition small signals in the presence of large common-mode voltages and DC potentials. The three op amp instrumentation amplifier architecture performs this function with the input stage providing a high input impedance while the output stage filters out the common mode voltage and delivers the differential voltage. This white paper discusses the basics of a three op amp instrumentation amplifier, examines the advantages of zero-drift amplifiers and programmable gain amplifiers, and reviews application examples for a sensor health monitor and an active shield guard drive.