Diodes, Transistors and Simple Circuits — O/L Science

Electronics deals with the controlled flow of electrons in circuits using semiconductor devices. Key components: resistor (limits current), capacitor (stores charge), diode (allows current in one direction only), transistor (amplifies signals or acts as a switch), and LED (emits light when forward biased).

Semiconductors (silicon, germanium) have conductivity between conductors and insulators. Doping adds impurities: n-type (extra electrons — phosphorus) and p-type (electron holes — boron). A p-n junction forms a diode. In forward bias (positive terminal → p-side), current flows; in reverse bias, no current.

Logic gates process binary signals (0 or 1). Basic gates: AND, OR, NOT (inverter), NAND, NOR. Truth tables define input/output relationships. Digital electronics underpins computers, mobile phones, and all digital devices — fundamental to modern technology and engineering.