Low-voltage transconductor with wide input range and large tuning capability

A CMOS triode transconductor was developed with common mode feedback suitable for operating in low-voltage and low-power applications. The design is based on a body-driven input stage with feedback loops to extend both the signal input range and the tuning capability. The effective transconductance of the body-driven triode stage is increased using a partial positive feedback technique which also partially solves the problem introduced by the small transconductance. This design uses the UMC 0.18 μrn CMOS process. Simulations show the transconductor operated with 1 V supply voltage has less than −55 dB total harmonic distortions (THD) in the complete tuning range (0 V ≤ V
cont
≤ 0.43 V) for a 1 MHz 0.8 V
p-p
differential input. The power consumption is 70 μW for a 0.43 V control voltage.