A CMOS-readout-amplifier for instrumentation applications

In recent years enormous progress has been made in integration of sensors and electronics on the same silicon substrate. Hence, a strong demand for incorporated instrumentation amplifiers has arisen. In this paper we present a fully integrated CMOS version of such an amplifier using switched-capacitor techniques. The amplifier system provides differential input capability, programmable amplification, clock generation, and low-pass filtering on the chip. The output signal is continuous in time and the system can be used without any of the special precautions necessary for sampled-data circuits. Emphasis was put on high PSRR (-63dB at dc), low noise (10-fVrms input equivalent wide-band noise) and offsets, low harmonic distortion, and small amplification error (<9.06% at 4 Vpp). To cover a large field of applications, only slightly different realizations can be used for capacitive sensors as well as for resitive sensor bridges.