What is a diode: – When P type semiconductor and N type semiconductor connected with each other than new formed device is known as PN diode which formally known a diode. Diode is a switch, which consist two terminal electronic components that’s why it is called diode. It has asymmetric transfer characteristic with low resistance to current flow in one direction, and high (ideally infinite) resistance in the other direction. A semiconductor material with a P-N junction connected to two material terminals.

 Need of a diode: – In areas of high frequency switching application where impossible to switch on & off manually at a very high speed like in power supply we need a switch which on or off at 50 Hz frequency to convert AC cycle to pulsating DC then a electronic switch required. As a result diode was discovered.

 Symbol of a diode: – Diode symbol define it’s characteristics if we analyze deeply, diode has arrow which indicated direction of current and a barrier which indicates current flow only single direction and appose in another direction.

Diodes Identification/numeric codes: –

In US by JEDEC (Joint Electron Device Engineering Council) in 1960s

1N is used for diode coding For Examples:

  •  1N 34A/1N 270 (Germanium)
  • 1N 914/1N 4148 (Silicon)
  • 1N 4001 to 1N 4007 (Silicon 1A power rectifier)
  • 1N 54xx (Silicon 3A power rectifier)

Diodes are reprinted by codes as


XN                                                 YYY

___                                                _____

Component                 identification number

X-number of semiconductor junctions

N-A semiconductor

YYY-identification number (order or registration number)

Also includes suffix letter (it applicable) to indicate

  1. Matching devices
  2. Reverse polarity
  3. Modification.