P-N junction diode as a rectifier

Half wave rectifier 

• When the P-N junction diode rectifies half of the ac wave, it is called half wave rectifier.

• During positive half cycle the diode forward biased and output signal is obtained
• During negative half cycle the diode reverse biased and output signal is not obtained
• Output voltage is obtained across the load resistance R_L. It is not constant but pulsating (mixture of ac and dc) in nature.
• Average output in one cycle 

• The R.M.S. output : 

• The ratio of the effective alternating component of the output voltage or current to the dc component is known as ripple factor.

• Efficiency: It is given by 

• Form factor : 
• The ripple frequency (w) for half wave rectifier is same as that of ac.

Full wave rectifier 

• It rectifies both half waves of ac input signal.
• During positive half cycle

1. Diode : D₁ forward biased
2. D₂ reverse biased

• Output signal obtained due to D₁ only
• During negative half cycle

1. Diode : D₁ reverse biased
2. D₂ forward biased

• Output signal obtained due to D₂ only
• Fluctuating dc ­­ ^filter   constant dc
• Output voltage is obtained across the load resistance R_L. It is not constant but pulsating in nature.
• Average output:
• Ripple factor: r=0.48=48%
• Ripple frequency: The ripple frequency of full wave rectifier = 2 x [Frequency of input cc]
• Peak inverse voltage (PIV): It’s value is 2V₀
• Efficiency:

 Full wave bridge rectifier 

• Four diodes D₁, D₃, D₃ and D₄ are used in the circuit.
• During positive half cycle D₁ and D₃ are forward biased and D₂ and D₄ are reverse biased
• During negative half cycle D₂ and D₄ are forward biased and D₁ and D₃ are reverse biased