An improved monolithic instrumentation amplifier

The design of an instrumentation amplifier fabricated using monolithic thin-film-on-silicon bipolar processing is described. The circuit features input as well as output overload protection, internal compensation, and improved noise and drift performance. A novel method of input-output signal coupling is described, which does not depend on tracking current sources, and provides a high degree of isolation for all but the desired signal components. The circuit is described in detail, and the layout techniques used to minimize thermal interaction are outlined. Finally, the performance of the circuit as typified by several production lots is reported.