Low-distortion super-GOhm subthreshold-MOS resistors for CMOS neural amplifiers

Abstract

A low-distortion super-GOhm subthreshold MOS resistor is designed, fabricated and experimentally validated. The circuit is utilized as a feedback element in the body of a two-stage neural recording amplifier. Linearity is experimentally validated for 0.5 Hz to 5 kHz input frequency and over 0.3 to 0.9 V output voltage dynamic range. The implemented pseudo resistor is also tunable, making the high-pass filter pole adjustable. The circuit is fabricated in 0.13-μm CMOS process and consumes 96 nW from a 1.2 V supply to realize an over 500 GΩ resistance.