23-08-2013, 04:03 PM
PN diode as a rectifier
PN diod.pptx (Size: 1.11 MB / Downloads: 26)
PN JUNCTION DIODE
A P-N junction is called as P-N junction diode or a semiconductor diode. This is also called as crystal diode because it is formed in a crystal[ Si or Ge].
A P-N junction diode is an unidirectional two terminal semiconductor device.
It conducts only in one direction & offers high resistance in other direction.
Application of P-N junction diode
Diode is used in rectifiers which are use in dc power supplies.
Diode is used as switch in logic circuit in computers
Diode is used in wave shaping circuit such as clippers & clappers.
Zener diode is used in voltage regulator circuit.
P-N JUNCTION AS A RECTIFIER
A rectifier is a circuit which is used to convert ac voltage into dc voltage.
A rectifier circuit uses one or more diodes
HALF-WAVE RECTIFIER FOR POSITIVE HALF CYCLE
During the positive half –cycle of the input voltage, the diode is forward biased, it conduct and a current – flows though the load resistance Rl to produce output voltage Vo. In forward-bias, the voltage drop across the diode is very small (0.7V for Si diode and 0.3V for Ge diode).
For practical purpose, we assume that diode is ideal so that the voltage across the diode is zero.
CENTRE-TAP FULL-WAVE RECTIFIER
THE centre-tap full wave rectifier circuit makes use of two diodes D1 & D2 Which are connected to the centre-tap secondary winding of the transformer.
Input a.c. voltage is applied to the primary of the transformer.
The voltage b/w one end of secondary and centre –tap is equal to half of the secondary voltage. This means that if the applied input voltage across the primary is V1 & across the secondary is V2 , then the voltage b/w one end of secondary & centre –tap is equal to V2/2.
FULL WAVE BRIDGE RECTIFIER
Bridge rectifiers uses 4 diodes which are connected across the secondary of the transformer .
Bridge rectifiers avoids the need of centre tape transformer