Question

What does the symbol for a transistor look like in a circuit diagram?

Answer 1

In a circuit diagram, the symbol for a transistor depends on the type of transistor being used. The two most common types of transistors are the bipolar junction transistor (BJT) and the field-effect transistor (FET). Each type has its own unique symbol:

Bipolar Junction Transistor (BJT):
There are two main types of BJT transistors: NPN and PNP. The symbols for these transistors are as follows:

NPN BJT:

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    E
    |
    |   NPN
    |
    B
   / \
  /   \
 /_____\
    |
    C


PNP BJT:

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    E
    |
    |   PNP
    |
    B
   / \
  /   \
 /_____\
    |
    C


In these symbols:

E: Emitter
B: Base
C: Collector

The arrow in the symbol points in the direction of conventional current flow from the collector to the emitter.

Field-Effect Transistor (FET):
The two main types of FET transistors are the N-channel (NMOS) and P-channel (PMOS) FETs. The symbols for these transistors are as follows:

N-channel (NMOS) FET:

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       N-Channel
         ______
Gate --|      |
         |      |
         |      |
         |______|
         |
       Drain


P-channel (PMOS) FET:

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       P-Channel
         ______
Source--|      |
         |      |
         |      |
         |______|
         |
       Gate


In these symbols:

Gate: Controls the flow of current between the source and drain.
Source: The terminal through which current enters the FET.
Drain: The terminal through which current exits the FET.

These symbols are used in circuit diagrams to represent transistors and show their connections with other components in an electronic circuit.