A wide tunable range CMOS OTA

A wide linear tunable range transconductor based on CMOS technology is proposed in this paper. The realization technique is achieved by squaring the transconductance gain (g_m) of the CMOS OTA. Its g_m can be linearly tuned by an external bias current for more than 3 decades (2 uA-3 mA), with less than 2% nonlinearity for the input-voltage linear range of about 1 Vp. The usefulness of the proposed linear tunable tranconductor is demonstrated through an application example, an electronically tunable biquad filter. The performance of the proposed circuit is discussed and confirmed through PSPICE simulation results.