Low power class d amp turorial

This article is intended for electronic hobbyist or students alike who are interested in learning the basic operating principle of these audio amplifiers popularly known as class D amp. These types of switching amps are ideally suited for battery operated gadgets and are popularly being used in cell phones, set top boxes, and most MP3 players due to its inherently high efficiency and low power consumption as opposed to linear amps. The sample circuit bellow is for low power headphone amplifier but can also drive small speakers as well.

The basic operating principles of these audio amps are similar to those of switching DC to DC converters utilizing PWM (pulse width modulation). But when used in audio applications, the output is purely in a clock pulses being modulated on its duty cycle in proportion to audio signal as a modulator.

Let’s say at chosen clock frequency of 200 kHz, the quiescent output pulses are at 50% duty cycle without audio but being modulated to +/- 50 when strong audio is present. This will yield an output of from 0 to 100% centered at 50. Continue reading “Low power class d amp turorial”