Feedback circuit of transistor amplifier 4

Considering the relationship between feedback signals and input and output circuits, negative feedback can be divided into four types: series voltage negative feedback,diode  series current negative feedback, parallel voltage negative feedback, and parallel current negative feedback. (2) Several commonly used negative feedback circuit diagrams 5-56 are amplification circuits that use emitter resistance RF for negative feedback. We use series current negative feedback here.diode  Lu is a negative feedback resistor for both AC and DC, typically using resistors ranging from tens of ohms to tens of ohms. Series current negative feedback increases the input and output impedance of the amplifier. Due to the increased input impedance of the amplifier,diode q can be chosen to be smaller. Generally, an electrolytic capacitor of 30-100uF can be used to meet the frequency response requirements of the amplifier's low-frequency end. Figure 5-57 shows a commonly used parallel voltage negative feedback circuit in amplifiers, where J represents the AC and DC negative feedback resistors. This negative feedback circuit is simple, which not only stabilizes the operating point but also improves the performance of the amplifier. Parallel voltage negative feedback will reduce the input impedance and output impedance of the amplifier. When using high-frequency transistors for low-frequency amplification,diode  a small capacitor ranging from tens of picofarads to hundreds of picofarads is often connected between the collector and base of the transistor to generate parallel voltage negative feedback on the high-frequency signal, eliminating the high-frequency self-excited oscillation that may occur in the transistor, diode as shown in Figure 5-58. Price can make the amplifier work stably and reduce noise.diode