Question

What is the BJT symbol?

Answer 1

The BJT (Bipolar Junction Transistor) symbol consists of three parts: the emitter, base, and collector. It has two types: **NPN** and **PNP** transistors.

1. **NPN Transistor**:  
   - The arrow in the symbol points **out** from the base to the emitter (because current flows out of the base to the emitter).
   - The collector is connected to the positive side of the circuit, and the emitter is connected to the negative side.

   **Symbol**:
   - A circle with three terminals:  
     - **Emitter (E)**: The emitter is the terminal from where the current leaves the transistor.
     - **Base (B)**: The base is the control terminal that regulates the transistor’s behavior.
     - **Collector (C)**: The collector is where the current flows into the transistor.

2. **PNP Transistor**:  
   - The arrow in the symbol points **in** to the base (because current flows into the base from the emitter).
   - The collector is connected to the negative side of the circuit, and the emitter is connected to the positive side.

   **Symbol**:
   - A similar circle with three terminals, but the direction of the arrow is reversed.

Here's how the symbols look:

- **NPN**:
  ```
       C
       |
       |
    B--|--> E
       |
  ```

- **PNP**:
  ```
       C
       |
       |
    B--|<-- E
       |
  ```

The current flows from the collector to the emitter in NPN and from the emitter to the collector in PNP transistors.