A CMOS transconductor with 80-dB SFDR up to 10 MHz

A CMOS transconductor uses resistors at the input and an OTA in unity-gain feedback to achieve 80-dB spurious-free dynamic range (SFDR) for 3.6-V-pp differential inputs up to 10 MHz. The combination of resistors at the input and negative feedback around the operational transconductance amplifier (OTA) allows this transconductor to accommodate a differential input swing of 4 V with a 3.3-V supply. The total harmonic distortion (THD) of the transconductor is -77 dB at 10 MHz for a 3.6-V-pp differential input and third-order intermodulation spurs measure less than -79 dBc for 1.8-V-pp differential inputs at 1 MHz. The transconductance core dissipates 10.56 mW from a 3.3-V supply and occupies 0.4 mm(2) in a 0.35-mum CMOS process.