Classification of power amplifiers

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Classification of power amplifiers [Copy link]

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

(1) Class A working state The collector current of the transistor is always flowing during the entire working cycle, as shown in Figure 9.1 (1). Class A working state is also called Class A working state. In this state, the amplifier has the lowest efficiency, but the nonlinear distortion is relatively small. It is 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 is off for the other half, as shown in Figure 9.1 (2). Class B working state is also called Class B working state. This amplifier generally has two complementary transistors working in push-pull mode. Its efficiency is higher than that of Class A amplifier, but there is a problem of crossover distortion. Generally, power amplifiers adopt this form.

(3) Class A and B working state This is a working state between Class A and Class B, that is, the transistor working cycle is greater than normal, as shown in Figure 9.1 (3). The characteristics of this power amplifier are between Class A and Class B.

(4) Class C working state In this state, the transistor works for less than half a cycle, as shown in Figure 9.1 (4). Class C working state is also called Class C working state. 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 adjusted to PWM form, the transistor works in the switching state, and the output end restores the signal waveform through LC filtering. The biggest feature of this power amplifier is its high efficiency, but the circuit is relatively complex and the high-frequency characteristics are poor. It is mainly used in miniaturization, battery power supply and high efficiency requirements.