Different classifications of power amplifiers

Jun 29, 2021

Power amplifiers are divided into the following four types according to their working conditions:

(1) Class A working state: The collector current of the transistor is always circulating during the entire working cycle, and the Class A working state is also called the Class A working state. The efficiency of the amplifier in this state is the lowest, but the nonlinear distortion is relatively small. Generally used in situations where contrast distortion is more sensitive, such as Hi-Fi audio.

(2) Class B working state: the transistor works for half a cycle, and the other half cycle is off. Class B working state is also called Class B working state. This type of amplifier generally has two complementary transistors for push-pull operation, and the efficiency is higher than that of a Class A power amplifier, but there is a problem of crossover distortion. Generally power amplifiers use this form.

(3) Class A and B working state: It is a working state between Class A and Class B, that is, the working cycle of the transistor is greater than normal. The characteristic of this kind of power amplifier lies between A and B.

(4) Class C working state: In this state, the working time of the transistor is less than half a cycle. Class C working status is also called Class C working status. Class C power amplifiers are generally used for high-frequency resonant power amplifiers.

(5) Class D power amplifier: In this type of amplifier, the input signal is first debugged in the form of PWM, the transistor works in the on-off state, and the output terminal is filtered to restore the signal waveform through LC. The biggest feature of this kind of power amplifier is its high efficiency, but the circuit is more complicated and the high frequency characteristics are poor. Mainly used for miniaturization, battery power supply and occasions requiring high efficiency.

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