New fully differential HF CMOS op amps with efficient common mode feedback

Conventional fully differential HF CMOS operational amplifiers (op amps) use an extra circuit to perform common-mode feedback (CMFB), which results in signal distortion and/or asymmetry as the signal swing increases. To solve this problem, two fully differential CMOS op amps that are based on merging two single-ended-output op amps are proposed and analyzed. Through the inherent differential-to-single-ended conversion circuitry, CMFB can be efficiently performed without extra circuits. The output signals are not distorted, and the HF performance is not degraded. Simulation and experimental results have confirmed the performance of the proposed new op amps