Choosing the Best Amplifier: Class A vs Class B vs Class A/B vs Class D Amplifiers

In any case, it’s not right. Tube amplifiers tend to produce 2nd order overtones and that is certainly not linear. It often becomes a pleasant experience.

The most technically perfect amplifier is a class A amplifier. It’s also dead simple to make with just a few components. However, Class A is so wasteful with energy that no one is going to build a powerful Class A, the amplifier would need enormous heat sinks.

Class B has a design with a transistor in the output stage for supplying and removing energy and is considerably more economical, but has a weak point when one transistor has to take over from the other.

Class A/B (popular from the 1970s to the 1990s): A modification of Class B by making both transistors conductive near the transfer point. Because both transistors are conductive, some energy is wasted (is converted directly into heat instead of driving the speaker), but the problem of the transfer point is largely solved.

Class D (popular from the 1990s): No longer a transistor that generates a continuous voltage, but MOSFETS that switch on or off. Pulse width modulation and a low-pass filter transform it into a continuous signal again. Class D amplifiers also have a weakness at the transfer point from the source MOSFET to the drain MOSFET, having both on at the same time would mean a short circuit, so the amplifier introduces a dead moment. Precisely because both switching on at the same time means a short circuit, the A/B trick of having both active for a short time is not possible.

Class D is extremely economical, can therefore be built in small chips and is therefore very popular in modern electronics.

2024-01-02 18:05:03
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