Linear Input Range Extension for Low-Voltage Operational Transconductance Amplifiers in Gm-C Filters

A second-order Gm-C low-pass filter with a novel large-signal linearization method for operational transconductance amplifiers having low supply voltages is presented. The design technique uses a combination of unbalanced resistively degenerated differential pairs and adaptive biasing to extend the linear range. The presented unity-gain biquad filter cell is intended to be used as a building block in the baseband section of a low-power receiver, and it has been designed in a standard 0.13-mu m CMOS technology with a cutoff frequency of 500 KHz. The power consumption of the filter is 39 mu W with a supply voltage of 0.6 V. Simulation results show a total harmonic distortion of -40 dB for a 5 KHz input tone with 614 mV peak-to-peak differential swing in the passband of the filter.