1.5 V large-driving class-AB buffer amplifier with quiescent current control - Electronics Letters

Introduction: The class-AB buffer amplifier is widely used for driving heavy resistive or capacitive loads [1–4]. Some buffer amplifiers employ a pseudo-source follower, which has a pair of complementary common-source transistors with two feedback loops consisting of a pair of complementary error amplifiers [1–2]. Employing error amplifiers introduces the excess phase shift and makes the frequency compensation complex. The other class-AB topology utilises an intermediate stage between the input differential pair and the output transistors [3, 4]. As the portable equipment is continuously growing and the circuit enters into the system on a chip (SoC) era, there is much demand to develop low-voltage buffer amplifiers. In this Letter, a 1.5 V large-driving class-AB CMOS buffer amplifier is proposed. The buffer achieves a large driving capability by employing two current mirrors, which also control the output quiescent current.