High-frequency offset-compensated CMOS current-feedback operational amplifier

A high-frequency current feedback operational amplifier (CFOA) with an on-chip current-mode input offset voltage compensation circuit is implemented in a 0.18μm CMOS process. The technique used to reduce the offset voltage is based on the variation of bias currents of the input buffer as a function of the detected error. Simulation results of the compensated CFOA, show 50% reduction of the input offset voltage, 71 dB open loop gain, 160 MHz bandwidth, and power consumption less than 1.5 mW from 1.8 V supply voltage. Measurements of 5 prototypes demonstrated the effectiveness of the compensation technique and the high-frequency performance of the designed CFOA. From these measurements we obtained a 70 dB open loop gain, a 152 MHz unity-gain bandwidth which is a little bit lower than the simulated one, and more than a 50% reduction of the input offset voltage.