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8-1
6-channel class-D amplifier
Basic operation of a class-D amplifier Basically, the output stage of a class-D amplifier outputs a continuous square wave swinging between positive and negative power supplies with a fixed frequency (�clock� frequency) far beyond the audible range. The duty cycle of this square wave is modulated with the audio signal. The output is followed by a low-pass filter which eliminates the clock frequency and allows only the audio signal going to the speaker. See simplified drawing below.
AMPLIFIER BOARD
TABLE OF CONTENTS Class-D Amplifier circuit description ................................................. 8-1 Exploded view + mechanical parts ................................................... 8-2 Amplifier circuit .................................................................................. 8-3 Clock Generator & connector - circuit ............................................... 8-4 Bottom view ....................................................................................... 8-5 Top view ............................................................................................. 8-6 Bottom view Part A ............................................................................ 8-7 Bottom view Part B ............................................................................ 8-8 Top view Part C ................................................................................. 8-9 Top view Part D ............................................................................... 8-10 Electrical parts list - Amplifier board ............................................... 8-11 The main disadvantage of this concept is: � The amplifier is operating with a high-frequency square wave at high amplitude and currents. This requires special precautions to prevent excessive electromagnetic radiation (EMC). Compared to a conventional power amplifier the benefits of the Class-D amplifier are: � higher effiency � lower power dissipation � smaller heatsink required � smaller mains transformer required
