Transistor amplifier circuit common base amplifier circuit common collector amplifier circuit 2

2. Co amplifying circuit

Transistor The input resistance of a common amplification circuit is large and the output resistance is small, but it only has current amplification capability and no voltage amplification capability. Generally, it is close to but less than 1. The AC path of a common amplification circuit is as follows.Transistor 

At first glance, it looks very similar to a collector amplifier circuit with no resistance at the emitter, except that the position of the AC ground is different. You can compare it yourself for easy differentiation. The formula for communication magnification is:Transistor 

From the formula, it can also be seen that the voltage amplification factor cannot be greater than 1. Usually, 1+β is very large, and then multiplied by a large resistor Re ', so this result is close to 1. In this formula, there is only one Re 'that is different from the formulas for the two amplification circuits above. Its value is equal to Re and is denoted by R L, while the other letters represent the same meaning as above.Transistor