Single-stage CMOS OTA for active-RC filter design

Single-stage operational transconductance amplifier is proposed for OTA-RC filter design. The concept is developed from a resistive source-degeneration long-tail pair where large transconductance is obtained by utilising negative resistance as a degeneration resistor. Such single-stage structure poses obvious advantage in consuming small current consumption compared to conventional two-stage OTA. Functionality of the proposed OTA has been confirmed by simulation of a complex 5^th-order Chebyshev channel-select filter in 0.18 mum CMOS process with centre frequencies of 1 MHz and 2 MHz for Bluetooth and ZigBee applications with respective in-band SFDR of 58 dB and 54 dB while draining static current consumption less than 450 muA from 1.5-V supply. The proposed OTA concept has also been experimentally verified with MOS transistor arrays implementation.