A control device provides a supply voltage to an output transistor of a power amplifier. The control device includes a detector encoder, a switch sequencer and a power switch. The detector encoder receives a detection signal indicating a negative peak voltage level of an output signal of the power amplifier, receives a reference signal indicating a critical voltage of the detection signal at which the negative peak voltage level of the output transistor is deemed to be out of voltage with reference to saturation voltage of the output transistor, compares the detection and reference signals, and outputs Boost Request and Recovery Request signals in response. The switch sequencer translates the Boost Request and Recovery Request signals into multiple control bits. The power switch coordinates switching among a no boost voltage and multiple boost voltages based on the control bits, and outputs one of these voltages as the supply voltage.