Diode vs Transistor
Semiconductor devices, illustrated
Diode vs Transistor
Not the same device — but a transistor has diodes hidden inside it
DIODE
One-way valve
1 PN junction, 2 terminals
Forward bias → conducts
Reverse bias → blocks
BJT NPN ／ Transistor
Current amplifier
2 PN junctions, 3 terminals
Small current Ib → controls large current Ic
Gain β = Ic ÷ Ib (can reach 100x+)
KEY INSIGHT
A transistor "contains" diodes, but it isn't a diode
| Property | Diode | Transistor (BJT NPN) |
|---|---|---|
| PN junctions | 1 | 2 |
| Terminals | 2 (A, K) | 3 (B, C, E) |
| Core function | One-way conduction, rectification | Current amplification, switching |
| Control method | Voltage polarity decides on/off | Small base current controls large current |
| Analogy | One-way check valve | Faucet (light touch, big flow) |