A Versatile Three-stage Operational Amplifier with Second-stage Bypass Compensation

A versatile three-stage operational amplifier with Second-stage Bypass Compensation scheme (SBC) is proposed. At high frequencies, the second stage is bypassed using a capacitive feed-forward path, reducing the amplifier to a two-stage one. Unity closed-loop gain stability is then ensured using a conventional two-stage compensation technique. Two single-ended topologies and one fully differential topology of the proposed amplifier are introduced. The proposed topologies allow operation with power-supply voltages as low as 1V and, therefore, are particularly suitable for use in low voltage, high gain designs using deep-submicron technology. Subsequently, simulation results of the single-ended and fully differential amplifiers and measurement results for two applications: (a) low-dropout regulator (LDO) and (b) low-pass filter (LPF) are presented. The applications were fabricated in UMC 65nm CMOS process.