DIODES AND RECTIFICATION

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  • Created by: Momo.
  • Created on: 02-03-13 13:30

What is a diode? 

DIODE CONVERTS AC TO DC
- made of semi-conducting material called silicon; low resistance in forward direction of diode so only allows current to flow in one direction
- needs 0.6V to start
- resistors are in series with diodes to protect them 

Semi-conductors
Semi-conductors contain delocalised electrons which allow current to flow.

It as two junctions..
HOLES: Abscence of electrons - P-TYPE
EXCESS OF ELECTRONS: More electrons than holes - N-TYPE 

Depletion zone/ layer- between two junctions and has no electrons or holes so no current can flow through it. (acts like an insulator)

REVERSE BIAS:
If the positive terminal of supply voltage is connected to n-type (junction with excess electrons) then the depletion layer widens as free charge (electrons) are attracted to opposite charge so move outwards.
The same happens for the p-type with the negative terminal of supply voltage. 

FORWARD BIAS:
If the positive terminal of supply voltage is connected to p-type (junction with holes) then the depletion layer narrows and dissapears. This is because like charges repel move towards the depletion layer. When it dissapears current can flow through the diode.
The same happens

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