🎚️ Transistor (BJT) Amplifier & Switch

📖 The Physics

A bipolar transistor has a superpower: a tiny base currentcontrols a much larger collector current. That is current amplification — the collector current is β (often 100–300) times the base current.

This holds as long as the transistor stays in its active region; push it too far and it saturates (fully ON) or, with no base current, cuts off (fully OFF).

The operating point (red) slides along the yellow load line. Low base current → bottom-right (OFF); raise it and it climbs the line into the active region; push further and it slams to top-left (saturated / ON) — the lamp is fully lit. That OFF/ON pair is how a transistor works as a switch (and builds logic gates).