1. Ensure that the transistor, the core device of the amplifying circuit, works in the amplifying state, that is, it has an appropriate bias. That is to say, the emitter junction is forward biased and the collector junction is reverse biased.
2. The setting of the input loop should make the input signal coupled to the input electrode of the triode to form a changing base current, thereby generating the current control relationship of the triode, which becomes the change of the collector current.
3. The setting of the output loop should ensure that the current signal amplified by the triode is converted into the form of electricity required by the load (output voltage or output current).