A continuous, low-glitch, low-offset, programmable gain and bandwidth Gm-C filter

Abstract

A programmable gain and bandwidth first-order low-pass Gm-C filter is proposed, designed, and simulated. Continuous low-offset operation is achieved by combining the continuity and low offset features of the ping-pong and auto-zeroing schemes. In the proposed strategy, clock feedthrough and charge injection are also reduced by decoupling the holding capacitor from the ac-signal path and increasing its value without affecting filter response. The ping-pong operation is designed to occur on the dominant pole-setting node, where a large capacitor resides, thereby also attenuating the glitches normally associated with "hand-over" events. The gain and bandwidth are programmed by adjusting the transconductance and loading resistance of the filter, achieving gain and bandwidth ranges and resolutions of 2-40 V/V, 75 mV/V, 1-5 KHz, and 32 Hz, respectively. Worst-case Monte Carlo simulations of the proposed 0.5 mum CMOS IC resulted in an input-referred offset of less than 0.5 mV and hand-over glitches below 5 mV