What Is an Audio Amplifier?
An audio amplifier is a circuit that raises a weak audio signal to the power needed to drive a speaker. It increases the signal's power while preserving its shape.
What Does It Do?
The signal from a microphone, phone or player is very weak; it can't move a speaker. The amplifier amplifies this signal to provide enough current and voltage.
Amplifier Classes
| Class | Efficiency | Property |
|---|---|---|
| A | Low | Cleanest sound, heats up a lot |
| AB | Medium | Good balance (classic hi-fi) |
| D | Very high | Switching, little heat |
Why Is Class D Common?
Class D switches the output transistors with PWM; it produces very little heat and provides high efficiency. So it's the standard in battery-powered and portable devices.
Where Is It Used?
Phone and tablet speakers, Bluetooth speakers, TV audio stages, car audio systems and home-theater amplifiers.
THD and Clipping
The basic metric of sound quality is THD (total harmonic distortion): it shows the unwanted harmonics the amplifier adds to the signal, and low THD means cleaner sound. As the amplifier approaches its power limit, the signal peaks get clipped and distortion rises rapidly; so the speaker and power are chosen to match.
Common Mistakes
- Impedance mismatch: the speaker impedance must match the amplifier (e.g. 4/8Ω).
- Power limit: overdriving causes distortion (clipping) and heat.
- Supply noise: a poorly filtered supply adds hum/interference to the sound.
Frequently Asked Questions
Does Class D sound bad?+
What does the wattage show?+
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