A class-D amplifier includes a loop filter, a pulse-width modulation (PWM) circuit, an output circuit, and a common-mode control circuit. The loop filter receives an input signal of the class-D amplifier to generate a filtered signal. The PWM circuit converts a non-PWM signal into a PWM signal, wherein the non-PWM signal is derived from at least the filtered signal. The output circuit generates an output signal of the class-D amplifier according to the PWM signal. The common-mode control circuit monitors a common-mode level of the output signal to generate a common-mode control signal for PWM common-mode control.

Certain aspects of the present disclosure provide methods and apparatus for adjusting a bandwidth of an amplifier (e.g., a programmable gain amplifier (PGA)). In certain aspects, the PGA generally includes at least one amplification stage having an input and an output, a plurality of compensation capacitors, and at least one first switch configured to selectively couple at least one capacitor of the plurality of compensation capacitors between the input and the output of the at least one amplification stage. In certain aspects, the amplifier includes at least one second switch configured to selectively couple the at least one capacitor to a node such that the at least one capacitor is coupled to only one of the output or the node, where a voltage at the node is a differential mode (DM) reference potential for the amplification stage.

A power amplifier using multi-path common-mode feedback loops for radio frequency linearization is disclosed. In one aspect, a complementary metal oxide semiconductor (CMOS) power amplifier containing cascoded n-type field effect transistors (NFETs) and cascoded p-type FETs (PFETs) may have a common-mode feedback network and provides bias voltages that are dynamically varying with the signal power to keep the output common-mode fixed around a half-supply level, while the small-signal and large-signal transconductances of the FET's are kept balanced. A further feedback network may be associated with the supply voltage to assist in providing a symmetrical supply signal. The symmetrical supply signal allows for supply variations without introducing distortion for the power amplifier stage.

A power amplifier using multi-path common-mode feedback loops for radio frequency linearization is disclosed. In one aspect, a complementary metal oxide semiconductor (CMOS) power amplifier containing cascoded n-type field effect transistors (NFETs) and cascoded p-type FETs (PFETs) may have a common-mode feedback network and provides bias voltages that are dynamically varying with the signal power to keep the output common-mode fixed around a half-supply level, while the small-signal and large-signal transconductances of the FETs are kept balanced. A further feedback network may be associated with the supply voltage to assist in providing a symmetrical supply signal. The symmetrical supply signal allows for supply variations without introducing distortion for the power amplifier stage.