Low-Power Class-AB CMOS Voltage Feedback Current Operational Amplifier With Tunable Gain and Bandwidth

A CMOS class-AB variable-gain voltage feedback current operational amplifier (VFCOA) is presented. The implementation is based on class-AB second-generation current conveyors and exploits an electronically tunable transistorized feedback network. The circuit combines high linearity, low power consumption, and variable-gain range from 0 to 24 dB with nearly constant bandwidth, tunable from 1 to 3 MHz. A prototype has been fabricated in 0.5-μm technology and occupies a total area of 0.127 mm
²
. The VFCOA operates using a 3.3-V supply with static power consumption of 280.5 μW. Measurements for maximum gain configuration show a dynamic range (1% THD at 300 kHz) of 87.5 dB and a THD lower than -40 dB for an output current 23 times the bias current.