What is the role of a DC power supply in an amplifier circuit?
The DC power supply in the amplification circuit is used to provide electrical energy to the amplifier. The amplifier amplifies the electrical signal by converting the electrical energy supplied by the DC power supply into an electrical signal that changes according to the input signal pattern. If the amplification circuit is not powered by a DC power supply, the amplifier will not be able to amplify electrical signals. Let's take a look at the following two simple amplification circuits.
The above figure shows a simple single tube AC amplifier. Rb is the base bias resistance of the 9014 transistor, Rc is the collector resistance of the transistor, RL is the load of the amplifier, and Es is the weak signal that needs to be amplified.
Ucc is a+9V DC power supply used to provide DC power to the entire amplifier circuit.
The AC signal Es that needs to be amplified is applied to the base of the transistor through the coupling capacitor C1. At this time, the c-e poles of the transistor can be regarded as a variable resistor that changes with Es. This resistor is connected in series with Rc to divide the+9V DC voltage. This will generate an electrical signal at the collector electrode (i.e. point c) of the transistor that follows the same pattern as Es but has a magnitude greater than Es. The signal can be applied to both ends of the load RL through the output coupling capacitor C2.
From this, it can be seen that if there is no DC power provided by the+9V DC power supply in this amplification circuit, the transistor will not work properly, and the amplification circuit will not be able to amplify electrical signals.
Not only do transistor amplification circuits require DC power supply to provide electrical energy, but amplification circuits composed of various ICs also require DC power supply to operate. The audio power amplifier circuit composed of LM386, as shown in the above figure, has a speaker as its load, and the function of LM386 power amplifier IC is to convert the electrical energy of the DC power supply into an audio signal with sufficient amplitude to drive the speaker to emit sound according to the input audio signal variation
