Understand it in 60 seconds · Components
The diode
Why did this board die? Its battery was plugged in backwards. A diode is a one-way flap for current: a little push opens it (about 0.7 V), a push backward slams it shut. One diode in series protects a board; four of them turn AC into DC, inside every charger.
Beginner · published 15 October 2026
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What you will understand
- A one-way flap for current: a little push opens it (about 0.7 V for silicon), a push backward shuts it.
- Current goes from anode to cathode only; the bar of the symbol is the band printed on the part. A Schottky opens at about 0.3 V, an LED at about 2 V.
- Backward it blocks, up to its breakdown voltage (often 50 V to 1000 V).
- One diode in the supply wire saves a board from a battery plugged in backwards. It costs 0.7 V, and P = 0.7 V × I.
- Four diodes make a bridge rectifier: two conduct on each half-wave, so the load always sees + on top; a capacitor fills the dips.
Inside the lesson
The cheat sheet
Every equation on one page, with the circuit drawn. Export it to PDF to keep it.
The animated presentation
The idea step by step, with the currents flowing in the circuit. Press Present (F5) to play it.
Your own copy
It opens as a Circuit Notebook project: change the values, reuse the circuit in your report.
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