Complementary Constant- $g_{m}$ Biasing of Nauta-Transconductors in Low-Power $g_{m}$ –$C$ Filters to ±2% Accuracy Over Temperature

This paper describes the design of an accurate and static complementary constant-
$g_{{m}}$
biasing circuit for Nauta's transconductors in low-power low-frequency CMOS
$g_{m}\mathchar"707B C$
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
$^{\circ}$
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.