A power amplifier may include a first amplifying unit receiving a first bias signal to amplify a power level of an input signal; an envelope detecting unit detecting an envelope of the input signal; a comparing circuit unit comparing a peak value of the detected envelope with a preset reference voltage; and a second amplifying unit amplifying the power level of the input signal according to a second bias signal set depending on a comparison result of the comparing circuit unit.

An open loop process and temperature independent bias circuit for stacked device amplifiers is disclosed herein. In one or more embodiments, a method for biasing a stacked high-voltage signal amplifier with a voltage divider bias module comprises generating, by the voltage divider bias module from a power supply voltage (VDD), a plurality of control voltage biases, which comprise a plurality of voltage references plus an offset voltage term (Vtemp). In one or more embodiments, the plurality of voltage references are each proportional to a division of the power supply voltage (VDD), and the offset voltage term (Vtemp) is proportional to temperature and is a function of process variation. The method further comprises biasing, a plurality of devices of the stacked high-voltage signal amplifier, with the control voltage biases.

A multiple-mode RF power amplifier includes two power amplifiers, output combiner circuitry, and a switchable impedance circuit. The power amplifiers receive first and second input RF signals and produce first and second amplified RF signals. The output combiner circuitry combines the amplified RF signals to produce a combined amplified RF signal. The switchable impedance circuit has an input terminal coupled to an isolated port of the output combiner circuitry. When the switchable impedance circuit is in a first state, the isolated port is coupled through the switchable impedance circuit to a first impedance to configure the multiple-mode RF power amplifier as a balanced amplifier. When the switchable impedance circuit is in a second or third state, the isolated port is coupled through the switchable impedance circuit to a second or third impedance to configure the multiple-mode RF power amplifier as a first or second type of Doherty power amplifier.