Transistor

[Annaaa]

A triode is a control element that is mainly used to control the magnitude of the current. Taking the common emitter connection as an example (signal from the base input, from the collector output, the emitter is grounded), when the base voltage UB has a slight change When the base current IB also has a small change, the collector current IC will have a large change under the control of the base current IB. The larger the base current IB, the larger the collector current IC.
Conversely, the smaller the base current, the smaller the collector current, that is, the base current controls the change in collector current. However, the change in collector current is much larger than the change in the base current, which is the amplification of the triode. The ratio of the amount of change in IC to the amount of change in IB is called the amplification factor β of the triode (β = ΔIC / ΔIB, Δ represents the amount of change.), the amplification factor β of the triode is generally tens to hundreds of times.
When the triode amplifies the signal, it must first enter the conduction state, that is, to establish a suitable static working point, also called the offset, otherwise the distortion will be amplified.
A resistor is connected between the collector of the triode and the power supply to convert the current into a voltage amplification: when the base voltage UB increases, the IB becomes larger, the IC also becomes larger, and the voltage drop of the IC at the collector resistance RC is also increased. Large, so the collector voltage UC of the triode will decrease, and the higher the UB, the lower the UC, ΔUC=ΔUB.
Is there any other role?