🔦 Triode Valve & Amplifier

📖 The Physics

In a triode valve, a hot cathode boils off electrons that stream up to the positive plate. In between sits a grid — a fine mesh whose voltage acts like a tap on the electron flow.

A small negative voltage on the grid repels electrons and throttles the plate current. Because the grid sits so close to the cathode, a tinygrid change causes a big plate-current change — that is amplification.

Nudge the grid voltage by one volt and watch Ip jump — that lever is the whole idea of an amplifier. Raising μ makes the grid an even more powerful control. The transistor later did the same job far more efficiently.