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A triangle pointing at a bar, marking a diode.
Also known as: Rectifier symbol, Triangle and line symbol, One-way valve symbol
A triangle meeting a flat bar marks a diode, and the drawing encodes its behaviour: current passes in the direction the triangle points and is blocked by the bar in the other. It is one of the few schematic symbols that explains itself.
Marks a diode: a component that allows current to pass in one direction and blocks it in the other.
Contexts: Electrical equipment
Encodes its own behaviour in its shape — conventional current flows in the direction the triangle points, and the bar at the triangle's tip represents the barrier in the reverse direction.
Contexts: Electrical equipment
Names its two terminals anode and cathode, the cathode being the barred end, which is marked on the physical component by a printed band.
Contexts: Electrical equipment
Takes modified forms for related components: a Zener diode bends the bar into a shallow Z, and a Schottky diode squares it into an S shape.
Contexts: Electrical equipment
Points the way current flows. The triangle is an arrowhead aimed at the bar, and conventional current passes in that direction and is blocked in the other; the bar is the cathode, and it corresponds to the printed band on the real component's body. A reader who remembers 'bar equals band' can orient a diode without a datasheet.
Contexts: Technical drawing, Electrical equipment
Related forms that are not treated as separate canonical symbols — see our variant rules.
Zener diode
The cathode bar bent back at both ends into a shallow Z. Designed to conduct backwards at a defined voltage, which is what makes it a reference rather than a fault.
Schottky diode
The cathode bar drawn with squared-off returns like a flattened S. A lower forward voltage drop and a faster recovery than an ordinary junction diode.
Photodiode
The diode with two arrows pointing *towards* it. The arrows always point the way the light travels, which is why they face inward here and outward on a light-emitting diode.
A solid triangle lying on its side with a short bar drawn across its pointed tip, perpendicular to the wire running through both.
The LED symbol is the diode symbol with two small arrows added; without them the two are identical.