DC suppressed high gain active CMOS instrumentation amplifier for biomedical application

A three op-amp active resistance instrumentation amplifier (I.A) with high gain and dc suppression is presented for biomedical applications. High gain is achieved by careful selection of aspect ratio of op-amps and by efficient design of passive resistances by active MOS transistors. DC suppression is achieved by offset cancellation circuit at the output of I.A. This offset cancellation circuit is built through suitable arrangement of transmission gate switches and capacitance. The proposed circuit has many interesting characteristics regarding low noise and simple design, while preserving common mode rejection ratio (CMRR) and high input impedance characteristics of the classical three op-amps I.A. The instrumentation amplifier is simulated using Cadence Spectre 500nm CMOS technology. It achieves an input-referred noise voltage of 22nV/√Hz, Gain of 45dB, Bandwidth of 5.8 KHz, CMRR in the range of 75dB and power consumption about 280μW, which is very good for biomedical signal processing application.