A Pulse Amplifier or Class-D Amplifier is a device that is used to supply either a wide range of power or a large amount of power to a device. This device can work with currents or with voltage. Generally it is used together with lasers for industrial purposes or to test scientific or military devices.

Class-D amplifiers work by generating a train of square pulses of fixed amplitude but varying width and separation, the low-frequency portion of whose frequency spectrum is essentially the signal to be amplified. The high-frequency portion serves no purpose other than to create a two level waveform. Because it has only two levels, it can be amplified by simple switching. The output of such a switch is an identical train of square pulses, except with greater amplitude. Such amplification results in a wave-form with the same frequency spectrum, but with every frequency uniformly magnified in amplitude.