The simplest triode audio amplifier circuit

0201 package SLP0603 ESD electrostatic diode 5V one-way ESD

Adjust the size of R1 so that the signal is not distorted at the maximum output, and R2 can output more power. If you have a multimeter, you can adjust the collector voltage of the triode to about 1/2 of the power supply voltage.

Figure 1 shows a fixed bias, the supply voltage has a large influence on the bias current. The voltage is negatively connected and the voltage range is wider. This class of class A amplification has the lowest efficiency and is characterized by simplicity. It is rarely used in low-voltage circuits because the output power is too small, and it is actually used in power-driven circuits while amplifying voltage and current.

In Figure 2, the bias is connected to the negative feedback, the amplification becomes smaller, and the power supply voltage has less influence on the bias current.