Transistor amplifier circuit common base amplifier circuit common collector amplifier circuit1

Transistor amplifier circuit common base amplifier circuit common collector amplifier circuit

Friends who have studied analog electronics should not be unfamiliar with the amplification circuit of transistor or field-effect Transistor (the amplification circuit mentioned in this article refers to voltage amplification). This is the key point in analog electronics, but it is also a difficult point. It is important to know for yourself, but if you cannot understand what is going on, it is okay. This time, taking the three configurations of transistor amplification circuit as an example, I will briefly explain the amplification factor calculation formula of amplification circuit.

The basic configuration amplification circuit composed of Transistor can be divided into three types, namely common emitter amplification circuit, common base amplification circuit, and common collector amplification circuit.

1. Common emitter amplifier circuit

The circuit schematic is as follows:

① The magnification factor is A=- Rc/Re. Design the values of Rc and Re according to the requirements. ② Input impedance: Zin=beta * Re. (R1 and R2 provide bias voltage for the transistor, which should be ignored here, but should be considered in practice). Due to the circuit amplification characteristics of the Transistor, Re needs to be amplified beta times when converted to the input terminal, resulting in a high input impedance. ③ Output impedance: Zout=Rc. In order to reduce the current of theTransistor and lower power consumption, Rc is generally taken at a large value. ④ Frequency characteristics: Due to the Miller effect, the parasitic capacitance between the base and collector of the transistor will be amplified by A times in the amplification region and reflected to the input terminal, resulting in poor frequency characteristics and inability to amplify high-frequency signals.