A Gate Leakage Feedback Element in an Adaptive Amplifier Application

This brief presents a method to exploit gate leakage (GL) to create a feedback element for an input offset insensitive and output offset programmable inverting amplifier. Measurements are shown from a test circuit produced in a 90-nm multithreshold CMOS process where a GL element uses thin oxide and a amplifier input stage uses thick oxide. The feedback element has very high nonlinear impedance from about 100 M$\Omega$ to several gigaohms depending on the applied voltage, and is suitable for adaptive applications where long time constants (1 ms to 1s) are required and small, slowly wandering offsets can be tolerated.