Class-AB rail-to-rail CMOS buffer with bulk-driven super source followers

This paper describes a rail-to-rail CMOS analog voltage buffer designed to have extremely low static current consumption as well as high current drive capability. The buffer employs a complementary pair of super source followers, but a bulk-driven input device with the replica-biased scheme is utilized to eliminate the DC level shift, quasi-floating gate transistors to achieve class-AB performance, and a current switch which shifts between the complementary pair to allow rail-to-rail operation. The proposed buffer has been designed for a 0.35 mum CMOS technology to operate at a 1.8 V supply voltage. The simulated results are provided to demonstrate that the total harmonic distortion for a 1.6 Vpp 100 kHz sine wave with a 68 pF load is as low as -46 dB, whilst the static current consumption remains under 8 muA.