Theoretical basis of power amplifier: the role
The power supply of the power amplifier should use the 'large water pool' filter capacitor. Because the large-capacity capacitor has a large inductance, a small-capacity capacitor should be connected in parallel to 'improve the speed of the power supply'. Is correct, but the theory of 'improving the speed of the power supply' is too vague. The author believes that the role of the filter capacitor in the power supply of the power amplifier has three functions: 1. Filter the rectified pulsed DC power to reduce AC interference. 2. High-speed power supply. 3. Provide a path for audio signals. The filtering effect of the capacitor on the power supply only shows whether there is AC interference to the power amplifier; the energy storage function of the capacitor can provide power for the transient high current of the power amplifier, but the transformer power is insufficient to charge it in time, its energy storage function It is not obvious; and it provides a path for the audio signal to affect the sound quality and timbre is also crucial. As shown in the positive half-cycle audio signal, the signal is divided into two channels through the power amplifier tube, the emitter resistor, the speaker, and the ground. One part forms a loop through the power transformer and rectifier, and the other forms a loop through the filter capacitor. Obviously, the inductance of the transformer is very large, which is not conducive to the passage of the high-frequency part of the audio. It can only pass the low-frequency audio signal with a very low frequency and can only provide a path for the subwoofer. More audio signals, especially the high-frequency part, pass through The power supply filter capacitor forms a loop. Capacitors and transformer secondary complement each other to provide audio frequency band path from DC to high frequency. Capacitors have parasitic inductance, which is undesirable. Inductance is not conducive to the passage of high-frequency signals. Generally, the larger the capacitance, the larger the volume, and the larger the inductance. Paralleling small-capacity capacitors can provide higher frequency bandwidth for the signal. path. 'Improve the speed of the power supply' is not correct in itself. The power transmission regardless of frequency is the speed of light. The only difference is that inductance and capacitance have an effect on the phase of AC. Filtering small-capacity capacitors in parallel uses the small inductance of small-capacitance capacitors to filter out interference waves other than 50 Hz.