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This paper describes the design of an accurate and static complementary constant-gm biasing circuit for Nauta's transconductors in low-power low-frequency CMOS gm-C bandpass filters and their optimization and trimming for process and temperature independent filter performance. Experimental results are presented for a prototype third-order Butterworth bandpass filter in a 180-nm CMOS process with a 2-MHz bandwidth and center frequency. These filters are appropriate for the channel selection stage of a Zigbee receiver and show with a single trim for process over a 120°C temperature range less than 2% deviation in the bandwidth and center frequency. Mismatch and process corner variation are demonstrated to have only a minimal effect on this performance.