A power encoder (600) includes a pulse width modulator (610) for modulating a signal (630) according to a set of thresholds (620) to produce a pulse width modulated (PWM) signal and a switch mode power amplifier for amplifying the PWM signal (615) by switching states of switching devices (650) according to amplitudes of the PWM signal. At least one or combination of a distribution of values of the voltage thresholds in the set and a distribution of values of a current generated by different switching devices are non-uniform. The set of voltage thresholds includes at least two positive voltage thresholds.