The LMC646x has the high input impedance, large common-mode range and high CMRR needed for designing instrumentation circuits. Instrumentation circuits designed with the LMC646x can reject a larger range of common-mode signals than most in-amps. This makes instrumentation circuits designed with the LMC646x an excellent choice for noisy or industrial environments. Other applications that benefit from these features include analytic medical instruments, magnetic field detectors, gas detectors, and silicon-based transducers.

A small valued potentiometer is used in series with R_G to set the differential gain of the three op-amp instrumentation circuit in Figure 7-11. This combination is used instead of one large valued potentiometer to increase gain trim accuracy and reduce error due to vibration.

A two op-amp instrumentation amplifier designed for a gain of 100 is shown in Figure 7-12. Low sensitivity trimming is made for offset voltage, CMRR and gain. Low cost and low power consumption are the main advantages of this two op-amp circuit.

Higher frequency and larger common-mode range applications are best facilitated by a three op-amp instrumentation amplifier.