Complementary constant-gm biasing of Nauta-transconductors in low-power gm-C filters to +/−2% accuracy over temperature

This paper describes the design of an accurate and simple static complementary constant-g_m biasing circuit for Nauta´s transconductors in low-power low-frequency CMOS g_m-C bandpass filters and their optimization and trimming for process and temperature independent filter performance. Experimental results are presented for a prototype 3^rd order Butterworth bandpass filter in a 180nm CMOS process with a 2MHz bandwidth and centre frequency. These filters are appropriate for the channel selection stage of a Zigbee receiver and show with a single trim for process over a 80C temperature range only a 2% deviation in the bandwidth and centre frequency.