A Diode is two terminal electrical device allowing current to move through it in one direction.

This unidirectional behavior is called rectification, and is used to convert alternating current to direct current.

Representation of diode…

1. Laser diode

2. Light emitting diode

3. Zener diode

4. Germanium diode

5. PIN diode

6. Silicon diode

7. Photo diode etc….

Diode in rectifier….

Rectification:-

Simply defined, Rectification is the conversion of ALTERNATING CURRENT(AC)to DIRECT CURRENT (DC).

Half wave rectifier:-This involves a device that only allows one-way flow of electrons. This simplest kind of rectifier circuit is half-wave rectifier.

It only allows one half of an AC wave form to pass through the load.

Full wave rectifier:-A Full Wave Rectifier is a circuit, which converts an ac voltage into a pulsating dc voltage using both half cycles of the applied ac voltage. It uses two diodes of which one conducts during one half cycle while the other conducts during the other half cycle of the applied ac voltage

Half wave rectifier Full wave rectifier

Zener diode….Zener Diodes are used in the "REVERSE" bias mode, i.e.

the anode connects to the negative supply, and from its

I-V characteristics curve

It is used in regulator, stabiliser, etc

Clippers are networks that employ diodes to “clip” away a portion of an input signal without distorting the remaining part of the applied waveform.

A clamper is a network constructed of a diode, a resistor, & a capacitor that shifts a waveform to a different DC level without changing the appearance of applied signal.

Clamping network have a capacitor connected directly from input to output with a resistive element in parallel with the output signal. The diode is also in parallel with the output signal but may not have a series DC supply as an added element.

LEDs emit light when an electric current passes

through them.

LEDs can be damaged by heat when soldering.

LED never connected directly through battery or power supply because instantly too much current will pass through and burn it out.

USES…Household appliances, VCR/ DVD/ Stereo/Audio/Video devices, Toys/Games Instrumentation, Security Equipment, Switches.

Mobile Phone, PDA's, Digital

Cameras, Lap Tops, General

Backlighting.

Etc…..

Photodiodes are semiconductor light sensors that generate a current or voltage when the P-N junction in the semiconductor is illuminated by light.

Features of photodiode

1.Excellent linearity with

respect to incident light

2.Low noise

3.Wide spectral response

4.Mechanically rugged

Uses….1. Dental science

2. Blood analysis

3. Cancer detection

4. DNA analysis

5. Machine vision

6. Range finding

7. X-ray film marking

etc….