Abstr: digital power amplifier is also called class D power amplifier. The main difference between digital power amplifier and analog power amplifier is the working state of power amplifier tube. There are class A and class B analog amplifiers. General small signal amplification is class a power amplifier. That is class A, the amplifier needs to be biased, and the amplitude of the amplified output should not exceed the offset range
The main difference between digital power amplifier and analog power amplifier is the working state of power amplifier tube. The traditional analog amplifiers include class A, class B, class A and class C, etc.
General small signal amplification is class a power amplifier. That is class A, the amplifier needs to be biased, and the amplitude of the amplified output cannot exceed the offset range, so the energy conversion efficiency is very low, and the theoretical efficiency is only 25%. Class B amplification. It is also known as class B amplifier. It does not need bias and relies on the signal itself to turn on the amplifier tube. The ideal efficiency is as high as 78.5%. However, due to such amplification, small signal distortion is serious, so the actual circuit should be slightly biased to form class A and class B power amplifiers, so the efficiency will be reduced. Although there is a class C amplifier in the high frequency transmitting circuit, that is, class C amplifier, which can be more efficient, but the circuit is complex and the sound quality is poor, so it is generally not used in audio amplification. The common feature of these analog amplifier circuits is that all transistors work in the linear amplification area. They control the output size according to the size of the input audio signal, just like a variable resistor in series between the power supply and the output to control the output, but it also consumes power. The power amplifier tube of digital power amplifier works in the switch state. In the theoretical state, when the transistor is on, the internal resistance is zero, there is no voltage at both ends, of course, there is no power consumption; and at the cut-off time, the internal resistance is infinite, the current is zero, and there is no power consumption. Therefore, as a control element, the transistor itself consumes power, and the utilization rate of power supply is particularly high.
The output of the switch transistor is pulse width modulation waveform. To become an audible analog audio signal, a low-pass filter with a bandwidth of 20 kHz is needed to filter out the high-frequency components in the pulse waveform. Generally speaking, the output voltage of the power amplifier is not a problem for the selection of capacitor withstand voltage, but the inductance is large and the allowable current should be designed correctly.
