Hybrid switching amplifier using a novel two-quadrant wideband buffer for dynamic power supply applications

A hybrid switching amplifier for dynamic power supply applications is presented. To achieve both high speed and high efficiency, a wideband buffered linear amplifier is combined with a hysteretic controlled switching amplifier. To obtain high linearity and reduce switching loss at low power levels where the switching amplifier is not needed, the linear amplifier supplies all load current with the switching one disabled. The novel two-quadrant linear amplifier as a voltage source for regulating the output voltage has very low output impedance of about 200 m Omega around the switching frequency, a high current-driving capability of maximum 220 mA and a bandwidth wider than 7 MHz. The hybrid amplifier can drive a circuit with an equivalent impedance of 7 Omega and supply a maximum output power of 1.1 W with a maximum efficiency of about 91%. Its output voltage ranges from 0.3 V to 2.9 V for a 3.3V supply. The chip is fabricated using only thick-oxide devices in a 0.13 um CMOS process and occupies an area of 3.9 mm².