Switching amplifier

[technoguy]

A switching amplifier or class-D amplifier is a power amplifier where the active devices (especially in the output stage) are operated in on/off mode (i.e., as switches). Output stages such as those used in pulse generators are examples of class D amplifiers. However, the term mostly applies to devices intended to reproduce signals with a bandwidth well below the switching frequency. These amplifiers use pulse width modulation (PWM), pulse density modulation (sometimes referred to as pulse frequency modulation) or more advanced forms of modulation such as Sigma delta modulation (see for example Analog Devices AD1990 Class-D audio power amplifier). The input signal is converted to a sequence of pulses whose average value is directly proportional to the amplitude of the signal at that time. The frequency of the pulses is typically ten or more times the highest frequency of interest in the input signal.