D is for Diode! Protector of circuits and the D in LEDs, learn how diodes work in this episode of Circuit Playground, featuring engineer Amanda “W0z” Wozniak and ADABOT. In the archives: Episode 1: A is for Ampere, Episode 2: B is for Battery, and Episode 3: C is for Capacitor. Save Video This feature is being tested. Saves will disappear if you clear cookies. Find saved videos here.