A CMOS transconductor with multidecade tuning using balanced current scaling in moderate inversion

A versatile CMOS transconductor is proposed. Voltage-to-current conversion employs a polysilicon resistor and features high linearity over a wide input range and high current efficiency. Programmable balanced current mirrors able to operate in weak or moderate inversion regions provide wide transconductance gain tuning range without degrading other performance parameters like input range and linearity. The transconductor has two degrees of freedom for gain tuning. A 0.5-μm implementation achieves a SFDR of 68 dB and a THD of -66.5dB using a dual supply of ±1.3 V with differential input swings equal to 77% of the total supply voltage, transconductance tuning over two decades, and 1.7 mW of static power consumption. Measurements demonstrate that operation in moderate inversion can lead to much less distortion levels than in strong inversion.