P-N JUNCTION
DIODE
HALF-WAVE RECTIFICATION
SMOOTHING OF RECTIFIED A.C.
VOLTAGE
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We know that A.C is particularly important. However, most electrical and electronics devices operate on d.c. sources only. Hence rectification of the A.C. is necessary. This can be done by using appropriate rectifiers and associated smoothing elements.
   
In Full Wave Rectification, we want to achieve this resultant output across R
  
  
from this
 
 
This can be done by using 4 p-n junction diodes connected in a bridge format (a bridge rectifier) as shown in diagram below:  

Explanation:  
  

During the positive half cycle of the input voltage (see the diagram below for actual current flow), when A is positive with respect to B, Diodes D1 and D2 are forward biased, while D3 and D4 are reverse liased. Hence D1 and D2 will conduct while D3 and D4 are off.The currect takes the path from A to D1 to D2 then to Load, R then to B, giving rise to an output voltage, which is approximately equal to the input voltage.
 

During the negative half cycle of the input voltage (see the diagram below for actual current flow), when A is negative with respect to B, diodes D1 and D2 are now off while D3 and D4 conduct. Hence the current will take the path of B to D3 to the load then to D4 and to A. Thus the current through the load is unidirectional and so is its output voltage (top positive with respect to bottom) 
  

This way, both halves of the a.c. voltage are rectified,and we have a full-wave rectified voltage across R! 
 

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