29/12/2019

DIODE Terminology : Forward bias, Break Over Voltage, Knee Voltage, Depletion Region, Doping


 Semiconductor diode
Ideal diode

  • It is diode which acts as a perfect conductor in the forward bias condition and insulator in the reverse biased conditions.
PN Junction
Charge Carriers
Forward bias
  • The DC voltage applied to the PN junction diode such that it cancels potential barrier completely and allowing current flows through it. 
  • The positive of the supply is given to anode ( P type semiconductor ) and negative is cathode ( N typesemiconductor ) in the forward biased condition.
Reverse bias
  • The DC voltage applied to the PN junction diode such that the potential barrier across it increases and current doesn’t allow through it. 
  • The positive of the supply is given to cathode ( N type semiconductor )   and negative is anode ( P type semiconductor ) in the forward biased condition.
Forward Resistance
  • The resistance offered at the PN junction during forward biased condition is called as forward resistance. 
  • The forward resistance of the ideal diode is zero and it is low for practical diode.
Reverse Resistance
  • The resistance offered at the PN junction during reverse biased condition is called as forward resistance
  • The reverse resistance of the ideal diode is infinite and it is very high for practical diode.
Depletion Region
  • The negative charge region created near the P type junction and positive charge region created near the N type region. This is called as depletion region.
Doping
Barrier Potential
  • The voltage across the depletion layer is called as barrier potential.
Breakdown Voltage
  • It is a minimum reverse voltage at which potential barrier of the PN junction breakdown and sharp current flows through it.
PIV ( Peak Inverse Voltage )
  • It is a maximum reverse voltage which the PN junction diode to withstand without damaging it.

Type of rectifier
PIV
Single Phase half wave Rectifier
Vm
Single Phase full wave rectifier
2Vm
Single Phase bridge rectifier
Vm

Knee voltage ( Turn on voltage )
  • It is a minimum forward voltage at which potential barrier of the PN junction breaks and current starts to flow through it.

Type of diode
Potential barrier
Silicon diode
0.7 V
Germanium diode
0.3 V
Ripple factor
  • The ripple factor indicates of effectiveness of DC component over AC component in the output of the rectifier. The details of ripple factor is given as below.
Filter circuit
  • The output of the rectifier is not DC but it contains some AC components. 
  • The function of the filter circuit is to remove AC component and allows only DC component to the output of the rectifier circuit.
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