The document discusses diodes, including their composition, operating principles, and applications in rectification processes. It outlines the characteristics of half wave and full wave rectifiers, detailing their functioning, advantages, and disadvantages. Key parameters such as ripple factor and voltage regulation are also described, along with comparisons between different types of rectifiers.

1. Diode

2. Contents
 P type layer
 N type layer
 Formation of Depletion layer
 Symbol
 Forward bias
 Reverse bias
 V-I characteristics of a Diode
 Applications
 Half wave Rectifier
 Full wave Rectifier
 Bridge Rectifier

3. Diode
 Diode is an electronic switch which conducts only during positive
cycle

4. Symbol

5. Atomic Structure of Silicon and Germanium
 Ge has a nucleus with 32 protons
the electrons are distributed as
2 in first orbit
8 in second orbit
18 in second orbit
the remaining 4 electrons are in
forth orbit
 Si has a nucleus with 14 protons

6. P type

7. N type

10. Formation of Depletion region

12. Barrier potential
 According to coulomb’s law, there
exist a force between these
opposite charges and this force
produce an electric field between
the charges.
 The induced voltage in depletion
region is called barrier potential
(or) threshold voltage (or) knee
voltage
= 0.3 for Ge

13. Forward Bias
Applied voltage > barrier voltage
 The diode acts as a closed switch
 This gives rise to uncontrolled forward
current through the diode.
 All the minority carriers flows move away
from the junction. They can’t form the
loop.

14. Reverse Bias
 All the majority carriers move away from
the junction. They can’t form the loop.
Depletion region increases
Junction resistance increases
 All the minority carriers flows through the
diode forming closed loop
 As the minority charge’s are very less
they form very low current called
reverse saturation current (or) leakage
current

15. V-I characteristics of diode

16. Types of Rectifiers
 Half wave rectifier
 Full wave rectifier
 Bridge rectifier
Rectifiers
A rectifier is a device which converts ac voltage in to pulsating
dc voltage, using one or more p-n junction diodes.

17. Half wave rectifier
 AC voltage across secondary terminals AB
changes its polarity after each half cycle.
 In Half wave rectification, the rectifier conducts
current during positive half cycle of input ac
signal only.
 Negative half cycle is suppressed.
 During the +ve half cycle:
 Terminal A becomes positive with respect to
terminal B.
 Diode is forward biased and act as short circuit.
Current flows in the circuit in the clockwise
direction for the full positive half cycle.

18. Half wave rectifier
 During the -ve half cycle:
 Terminal A becomes negative with respect to
terminal B.
 Diode is reverse biased and acts as open circuit.
Hence no current flows in the circuit. Thus the
circuit current, which is also the load current, is in
the form of half sinusoidal pulses.

19. Output Parameters of half wave rectifier
 Average voltage
 Average output current

 RMS voltage
 Peak inverse voltage =
 Form Factor =
 Peak factor =

20. Ripple Factor
 It is seen that the output of half wave rectifier is not pure DC but a pulsating DC. The
output contains pulsating components called ripples. Ideally there should not be any
ripples in the rectifier output. The measure of such ripples present in the output is with the
help of a factor called ripple factor denoted by γ. It tells how smooth is the output.
 Mathematically ripple factor is defined as the ratio of RMS value of the a.c component in
the output to the average or d.c component present in the output.
Ripple factor =
Now the output waveform is composed of a.c component and d.c component

21. Ripple factor =
γ =
γ =
now for a half wave rectifier circuit,
,
Therefore, γ = 1.211
This indicates that the ripple contents in the output are 1.211 times the dc
component

22. Voltage regulation
 The secondary voltage should not change with respect to the load
current. The voltage regulation is the factor which tells us about the
change in the dc output voltage as load changes from no load to
full load condition.
Voltage regulation =
Where ,
= DC voltage on no load
= DC voltage on full load

23. Output Parameters of half wave rectifier
 Average voltage
 RMS voltage
 Ripple factor = 1.211
 Peak inverse voltage =
 Form Factor =
 Peak factor =

24. Advantages
 Simple circuit
 PIV =
Disadvantages
 Efficiency is less
 Ripple factor is greater than 1
To over come the disadvantages of HWR we use full wave rectifier

25. Full wave rectifier with center tap
transformer
Output Parameters
 Average voltage
 RMS voltage
 Ripple factor = 0.483
 Peak inverse voltage =
 Form Factor =
 Peak factor = 1.414

26. Advantages
Disadvantages
 Efficiency is more
 Ripple factor is less than 1
To over come the disadvantages of center tapped FWR we using full wave bridge rectifier
 Center tapping transformer is difficult
 PIV =

27. Full Wave Bridge Rectifier

28. During +ve half cycle
 During +ve half cycle i.e from
period t=0 to t=T/2 D2 and D3 are
conducting while D1 and D4 are in
the “off” state.

29. During -ve half cycle
 During -ve half cycle i.e from period
t=T/2 to t=T D4 and D1 are
conducting while D2 and D3 are in
the “off” state.

30. Advantages
Disadvantages
 Efficiency is more
 Ripple factor is less than 1
 No need of center tapping transformer
 PIV =
 Required 4 diodes

33. Half wave rectifier Center tapped
transformer
Full wave rectifier
No.of Diode
used
Ripple Factor
PIV
Peak inverse
voltage
1
1.211
2
0.483
4
0.483