Design of a Linear Class AB Amplifier with 55dB Gain, 890MHz Bandwidth and Low Output Impedance for Envelope Tracking Supply Modulator

This paper presents a linear class-AB amplifier for envelope tracking of polar modulation. In this amplifier, by maintaining the phase margin, the capacitor size of the compensator is reduced, while a high gain-bandwidth is obtained. Hybrid Supply Envelope Modulator (HSEM) requires high gain-bandwidth, high slew-rate and low output impedance. In this work, due to low output impedance, the HSEM architecture is capable of reducing the switching noise up to 76MHz. Furthermore, owning to high slew-rate and high gain-bandwidth, the HSEM can quickly track the envelope of signal. Simulation of the proposed amplifier in 180 nm CMOS technology illustrates 55dB DC gain, 890 MHz gain-bandwidth, 1492 / 1518 [V/(μs)] slew-rate, and maximum output impedance of 0.9880 below 76MHz.