Patent ID: 8472643

Claim:
An improved power amplifier, comprising: an input amplifier unit, being coupled to an input source to receive input signals and configured to amplify the input signals to output amplified signals; at least one pulse modulation unit, being coupled to the input amplifier unit to receive the amplified signals and configured to perform pulse modulation on the amplified signals to output pulse-modulated signals; at least one pre-drive unit, being coupled to the pulse modulation unit to receive the pulse-modulated signals and configured to control a circuit unit of a next stage according to the pulse-modulated signals; at least one output stage transistor set, being coupled to the pre-drive unit, wherein the pre-drive unit receives the pulse-modulated signals outputted by the pulse modulation unit and, according to the pulse-modulated signals, controls the on/off status of the output stage transistor set so that the output stage transistor set outputs power signals; a power amplifier positive output terminal, being coupled to the output stage transistor sets to receive the power signals for driving a load; a power amplifier negative output terminal, being coupled to the output stage transistor set to receive the power signals for driving the load; and an output power restraint unit, being coupled between the power amplifier positive output terminal, the power amplifier negative output terminal and the input amplifier unit to receive the power signals and restrain power of the improved power amplifier, the output power restraint unit comprising: an oscillation wave transformation unit, being configured to generate oscillation wave signals and output a charging capacitor voltage; and a power signal transformation unit, being coupled to the oscillation wave transformation unit, the power amplifier positive output terminal and the power amplifier negative output terminal, and being configured to transform the power signal into a logic capacitor voltage for comparison against the charging capacitor voltage outputted by the oscillation wave transformation unit, wherein when the logical capacitor voltage exceeds the charging capacitor voltage, it means that the output power is excessively high, in which case the power signal transformation unit feeds back a signal to the input amplifier unit to decrease an output gain, thereby restraining the power by decreasing the output gain of the input amplifier unit.