At the input terminal: If the feedback signal and the input signal are connected to the same input terminal, the calculation is in the form of current, which is negative feedback of current. If the feedback signal and the input signal are connected to different terminals of the a

1. Prepare circuit

negative feedback circuit basic knowledge:

connect the circuit from the input terminal to the negative feedback circuits into voltage negative feedback and current negative feedback. The simplest way to distinguish is:

at the output terminal

• If the feedback sampling point at the output terminal is at the same point as the output, it is voltage feedback;
• is not at the same point, it is current feedback.

at the input terminal :

• If the feedback signal and the input signal are connected to the same input terminal, the calculation is in the form of current, which is negative feedback of current.
• If the feedback signal and the input signal are connected to different terminals of the amplifying circuit , then the calculation is in the form of voltage, which is negative feedback of voltage.

current negative feedback bias circuit has good temperature stability. Selecting the appropriate bias resistor resistance value and designing the DC working point can make the amplifier circuit work stably and reliably. This paper analyzes the series current negative feedback static voltage analysis, and prepares the following NPN transistor circuit.

. Calculation process . Calculation of B-pole voltage

B pole current is much smaller than the current of Rb1-Rb2 path. Assume I_bI_{Rb}, ignore the influence of B-E junction and calculate the B-pole voltage:

If the B-E junction current is calculated, V_B is slightly less than 2.5V.

. Calculate the E-electrode current

B-E voltage drop is about 0.6V, and get:

. Calculate the B-electrode current

, you need to know the amplification factor of transistor , here assume that the amplification factor of the transistor is 100.

. Calculate the C-pole current

. Calculate the C-pole voltage

Similarly, if the current requirements for each point are given, the required resistance values ​​can also be calculated.