The pinout of transistors varies depending on the type. There are mainly two types of transistors: bipolar junction transistors (BJTs) and field-effect transistors (FETs).
Bipolar Junction Transistors (BJTs):
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NPN type:
- Emitter (E): It is the electrode through which current flows out of the transistor. In an NPN transistor, the emitter mainly emits electrons. These electrons, under the control of the base current, pass through the base region and reach the collector to form a current. For example, in a simple amplification circuit, the input signal is connected to the base, and the emitter is usually connected to ground.
- Base (B): The base controls the flow of current between the emitter and collector. By applying a small input current to the base, it can regulate the larger current flowing between the emitter and collector.
- Collector (C): It is the electrode where the majority of the current flows into. In an NPN transistor, the collector collects the electrons emitted from the emitter.
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PNP type:
- The functions of the emitter, base, and collector are similar to those of the NPN type, but the directions of current flow are reversed.
Field-Effect Transistors (FETs):
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Junction Field-Effect Transistors (JFETs):
- Source (S): It is the electrode where the majority carriers originate.
- Gate (G): The gate controls the conductivity between the source and drain by varying the electric field.
- Drain (D): It is the electrode where the majority carriers flow out.
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Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs):
- Similar to JFETs, they have source (S), gate (G), and drain (D) pins. However, MOSFETs can be further divided into N-channel and P-channel types, and their characteristics and applications are different.
Understanding the pinout of transistors is crucial for correctly using them in electronic circuits.