Diode

Passes current in one direction.

Schematic letter: D
Unit / key rating: Current (A), reverse voltage (V)

Pinout

Anode: The side without the stripe.
Cathode: The side with the grey/white stripe on the body.

Real photos

1N4007 rectifier diodes; the stripe marks the cathode

What is it for?

A diode passes current only from anode to cathode. A silicon diode drops about 0.7 V while conducting.

It is used to turn AC into DC (rectification), to protect against reverse polarity and to absorb voltage spikes from relays.

Things to watch out for

⚠ The 1N4007 is a general-purpose diode and the 1N4148 a fast signal diode. They can't always replace each other.

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