4. NPN Transistors

Step 1: Breadboard the circuit

Step 2: Open Falstad simulation

Step 3: Questions


Falstad Circuit Simulator: NPN Transistors

Transistors are like switches that use a small current to turn them on.

Inside, they are very similar to diodes. The arrow shows direction of current and differentiates the 3 pins:

  • Collector: Primary input – provides current
  • Base: Second input – turns on/off
  • Emitter: Output

When the base receives a small current, the NPN transistor allows current to flow from the collector to emitter.


Theory 4

1. What happens when the resistor (10k) connected to A is removed?

2. Is A or B the main source of current? (checkĀ Falstad)

3. What happens if you flip the direction of the transistor?

4. Why does the base have a 10k resistor, but the emitter and LED have a 220Ī©.