Correctly analyze the role of discrete components in the circuit - resistors, capacitors, inductors, diodes, transistors (I)

When reading electronic circuit diagrams, it is necessary to correctly analyze the role of discrete components in electronic circuits.

In order to facilitate the reading of the circuit diagram, the roles of the different components in the electronic circuit and the connection of the different components should be summarized as follows:

resistance:

The resistor mainly plays a role of current limiting, voltage division, voltage drop and the like in the circuit.

1. Resistance and resistance are connected in parallel in the circuit in general to increase the power of the resistor.

2. The resistor is connected in series with the resistor and leads from the middle. In general, it is to obtain the partial pressure on the resistor.

3. The resistor is connected in series with the Zener diode, and is generally used as a current limiting resistor of the Zener diode.

4. The resistor and capacitor are connected in series to form a differential circuit. At this time, the resistor acts as a charge current limiting resistor of the capacitor, and the charging constant is determined by the product of RC. If the differential circuit is connected in parallel with a transistor device such as a diode or a unidirectional thyristor, and there is an inductive load in the circuit, the differential circuit functions as a resistance-capacitance absorption in the circuit, that is, the absorption inductor is generated at a high speed in the startup and shutdown. The induced electromotive force protects the transistor device from breakdown damage due to too high induced electromotive force.

5. The resistor is connected in parallel with the capacitor. In general, as the discharge resistance of the capacitor, the discharge constant is also determined by the product of RC.

6. The resistor is connected in parallel with the inductor, and the resistor is the discharge resistor of the inductor.

7. In the amplifying circuit, the resistor is connected to the base of the transistor, which is generally the bias resistance of the base of the transistor; the collector load resistor is connected in series with the collector; and the emitter resistor is connected in series with the emitter. R11 and R12 are the base bias resistors; R13 is the collector load resistor; R14 is the emitter resistor.

Capacitor:

The main role of capacitors in the circuit is energy storage, filtering, and so on. It is characterized by AC and DC.

1. The capacitor and the inductor are connected in parallel to form a resonant circuit (LC oscillating circuit).

2. The capacitor is connected to the input and output terminals of the transistor amplifying circuit, and the capacitor functions as an input and output coupling. In the "resistor-to-transistor connection" circuit above, C4 is the input coupling capacitor and C6 is the output coupling capacitor.

3. The capacitor is connected in series with the emitter of the transistor, and generally functions as an AC bypass. In the "resistor to transistor connection" circuit above, C7 is an AC bypass capacitor.

4. At the input end of the amplifying circuit, the capacitor is connected in parallel with the input signal, generally acting as an anti-interference signal. In the "resistor to transistor connection" circuit above, C3 is the input anti-interference capacitor.