High-drive CMOS current amplifier

A high-performance current amplifier is proposed which is based on a folded-cascode transresistance amplifier and a low-distortion class AB current output stage. The loop gain of the transresistance amplifier exhibits a gain bandwidth product of 10 MHz and a DC gain as high as 100 dB which allows accurate closed-loop operations to be achieved. Despite the intrinsic low-linearity performance of current amplifiers with respect to their voltage amplifier counterpart, the proposed circuit provides an output current of 7 mA with a total harmonic distortion (THD) better than -55 dB while requiring only 200 μA of quiescent current for the output transistors. The circuit was fabricated in a 1.2 μm CMOS process, uses a 5 V power supply, and dissipates 4 mW