Question

What is collector in BJT?

Answer 1

In a **BJT** (Bipolar Junction Transistor), the **collector** is one of the three terminals — the others being the **emitter** and the **base**.

Here’s a clear explanation:

- The **collector** is the region of the BJT that **collects the majority of the charge carriers** (electrons or holes) that are injected from the emitter through the base.
- It is typically **larger and more heavily doped** compared to the base (but less doped than the emitter) to handle **higher voltages and dissipate more heat**, because most of the current flowing through the BJT exits via the collector.
- In circuit operation:
  - In an **NPN transistor**, the collector is **positive** relative to the emitter.
  - In a **PNP transistor**, the collector is **negative** relative to the emitter.

**Summary of its role:**
- The collector "collects" carriers from the emitter via the base.
- It is mainly responsible for allowing a **large current flow** controlled by the small base current.
- It connects to the **higher voltage side** of the circuit (in NPN) or **lower voltage side** (in PNP).

**Visual structure:**
```
NPN Transistor:
Emitter (N) → Base (P) → Collector (N)

PNP Transistor:
Emitter (P) → Base (N) → Collector (P)
```

Would you also like a quick diagram or a basic working example of a BJT to make it even clearer?