Linear compact CMOS OTA with multidecade tuning, -62dB IM3, -75dB SFDR, constant input range and two independent degrees of freedom for gain adjustment

Two versions of a compact and highly linear CMOS OTA, with two decades gain tuning range are presented. They use a fixed gain linear V-I conversion input stage and electronically programmable current mirrors working in triode mode. Programmability is achieved by tuning the drain-source voltage of the mirroring transistors. The OTA input range is independent of gain adjustment. Experimental results of a test chip in 0.5mum CMOS technology validate the OTA characteristics with distortion less than 0.5% over the entire tuning range