The parts that don’t need power to work.

Passive components handle energy without amplifying it. They make up most of any board, and they’re the parts you’ll pick and size yourself.

1. 1Resistors & potentiometersInteractiveHow resistors set current and divide voltage, what tolerance and power rating actually constrain, and where a potentiometer earns its place.1 min read·2 questions
2. 2CapacitorsCapacitors store charge and resist voltage change. Ceramic, electrolytic and tantalum compared, plus what capacitance derating means in practice.1 min read·2 questions
3. 3Inductors & transformersInductors resist changes in current and store energy in a magnetic field. Saturation, DCR, and how transformers move energy across an isolation barrier.1 min read·2 questions
4. 4Diodes & LEDsInteractiveDiodes conduct one way. Forward voltage, reverse breakdown, Schottky and Zener behaviour, and how to drive an LED without cooking it.1 min read·3 questions
5. 5Fuses, crystals & oscillatorsFuses and PTCs protect a board from its own faults; crystals and oscillators give it a time reference. Load capacitance, ppm, and when to pay for an oscillator.1 min read·2 questions