Principle of composition of the amplifying circuit
1. Ensure that the core device of the amplifier circuit operates in an amplified state, that is, it has a proper bias. That is to say, the emitter junction is positively biased, and the collector junction is reverse biased.
2. The input loop should be set such that the input signal is coupled to the input electrode of the triode to form a varying base current, resulting in a current control relationship of the triode that becomes a change in collector current.
3. The output loop should be set to ensure that the current signal after the transistor is amplified is converted to the form of charge (output voltage or output current) required by the load.