A 30pA/V 25 ? A / V linear CMOS channel-length-modulation OTA
A fully balanced highly linear CMOS operational transconductance amplifier (OTA) is presented. The proposed circuit combines a cross-coupled channel length modulation cell with a tunable-gain current mirror. Good linearity over a wide tuning range is achieved. As an example, the OTA has been used in designing a second-order tunable VCO. Both the OTA and the VCO have been fabricated in the AMS 0.35 ? m CMOS process. Measured results show that the transconductance of the OTA ranges from 30pA/V to 25 ? A / V , and the VCO achieves a tuning range from 6Hz to 180kHz.
cmos operational transconductance amplifier channel length modulation wide tuning range vco