How to Read Diode Numbers
By James Miller
The system for categorizing diodes, one of the electronic components on circuit boards, follows the U.S. Joint Electron Devices Engineering Council (JEDEC) numbering scheme. There are many styles of diodes. The most common ones in everyday electronics are rectifier diodes, which convert alternating current (AC) to direct current (DC).
Verify you are looking at a diode. Diodes have two "leads" -- contacts or wires that connect to the circuit board.
Note the polarity. Much like a battery, a diode has a polarity. The negative side, or cathode, is usually represented by a bar, band or line along one end of the component body. It may also be marked with a "K" or by a raised or tapered edge. The positive side, or anode, typically has no marking.
Decode the diode type and material designation. This is designated by the "1N" in the part number. The "1" identifies the component as a diode. The "N" shows the material in the device is a semiconductor.
Decode the model code. The number after the diode and material-designation codes is the model or part number. There are thousands of diode styles. Examples include 1N4148, which identifies a high-speed general rectification diode; 1N914, a general-purpose model; and 1N4973, a voltage-regulator diode.
- The best way to understand the part number for a particular diode is to look at a datasheet for the component. You can often find one on the website of an electronic-parts supplier.
- Before removing a diode from a circuit board, use a fine-tipped marker to designate the cathode side by making a small line on the printed circuit board.
- Inserting a diode incorrectly can cause failure of electronic components, including overheating, which can cause burns.
James Miller is an Electrical Engineer who has experience in OEM electronic equipment and PLC programming. As a sideline he dabbles in real-estate investing, Web development and programming. He writes instructional articles for various websites.