A novel CMOS operational transconductance amplifier based on a mobility compensation technique

This brief describes a new linear operational transconductance amplifier (OTA) and its application to a ninth-order Bessel filter. To improve the linearity of the OTA, we employ a mobility compensation circuit which combines the transistors operating in the triode and the subthreshold regions. The proposed technique enhances the linearity of the transconductance without loss of the input swing range. The proposed OTA shows +/-0.5% Gm variation and the total harmonic distortion of less than -60-dB over the input range of +/-0.8-V. The ninth-order Bessel filter employing the proposed OTA has been implemented in a 0.35-mum n-well CMOS process under 3.3-V supply voltage. It shows the cutoff frequency of 8 MHz and the power consumption of 65 mW.