Build a Class D audio amplifier

July 25, 2016 | 14:08
Build a Class D audio amplifier
Build a Class D audio amplifier
Compared to analog audio amplifiers like Class-A, -B and -AB, digital Class-D amplifiers have much higher power efficiency allowing them to run cooler and longer from a battery, which is why they have become very popular in portable equipment like phones and MP3 players, but also in many other applications. Even though Class-D amplifiers have their negative points, bad EMI behavior for instance, most of these problems can be fixed more than satisfactory by applying good design techinques and practices. Here is a design for a full-bridge Class-D amplifier that, contrary to a half-bridge design, does not produce even harmonics.

Besides being a full-bridge design, or balanced as the author calls it, the amplifier also has a balanced input. Constructed as a self-oscillating PWM modulator with two push-pull power output stages to form the bridge, the amplifier sports a -3 dB bandwidth of 7 Hz to 70 kHz and can deliver up to 30 watts into an 8 ohms loudspeaker.

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