Use of guard rings in solving cross talk problems between analog VLSI based instrumentation amplifiers

In this work, a quad instrumentation ampliJier VLSI chip was designed for minimum cross talk reduction for a multi-channel data acquisition cardiac diagnostic system that requires high attenuation of the cross talk between channels. Since the cross talk problem was related to parasitic bipolar junction transistors, an approach was followed to isolate the input terminals using quad rings. Four diflerent chips were designed, fabricated, and tested against the simulation and calculated performance. The differential-mode voltage open loop gain was designed to provide 7 .95~16 with a CMRR of 82.9dB. MOSIS service for analog CMOS NWell process was used, considering f2.W power supply to minimize power consumption. Cross talk attenuation in excess of 90 db was recorded between channels.