On-chip active guard band filters to suppress substrate-coupling noise in analog and digital mixed-signal integrated circuits

An AC coupling configuration of active guard band filters can supply a substrate-coupling-noise cancellation signal to a ground-level substrate by using a single 3 V supply to on-chip circuits. Noise was suppressed to a maximum of less than 0.05 from 100 Hz to 2 MHz in a 0.35 /spl mu/m CMOS test chip. Experiments and a simulation based on the substrate model showed that the noise-suppression effect depends on the guard-band arrangement. The simulation is thus effective for optimizing the arrangement to strongly suppress noise effects.