P-N junction diode is a semi Conductor device with two forminals, typically allowing the flow of current in one direction only that's called p-n junction diode.
If P-type at one end of the pure semiconductor and N-type at another end of the same pure semiconductor is fitted , it is called P-N diode. In normal position there is no reaction but if some kind of emission is there, the flow of electrons starts in P-N diode. It has two terminals one is cathode and another is anode . used of p-n junction diode is two types one is forward baised type and another is reverse based
p - n junction diode has two side one is left side and another is right side. the left side junction has P-type crystal consistes of the majority charge carrier holes and immobile acceptor ions indicated by negative sign as after accepting an electron it becomes negative . other side of junction the N-type semi-conductor consists of charge carriers as electrons and the immobile donor ions having positive sign, because after a donor atom donates an electron, it becomes positive ions.
the P-type crystal also the electrons as majority carriers and N-type has the holes as majority carriers.
the connection of p - n junction diode is two types in circuit
1.forward based 2. reverse based
1.forword based : The voltage potential is connected positive, (+ve) to the P- type material and negative, (-ve) to the N-type material across the diode which has the effect of Decreasing the PN junction diodes width. This forward biased pushes the majority carriers to cross the junction as positive potential pushes the holes. The internal potential at starting is very small to control, thus, allow the large current to flow in forward direction .
applied voltage the reduction is built in potential which force move electrons into N-type region and more holes into P-type region, thus covering some of the fixed charges and narrowing the depletion layer, which reduce the uncovered charge and lower the build-in potential. Since the build-in potential opposes the flow of majority carriers across the junction, thus it makes easier for holes in the P-type region and for electrons in the N-type region to cross the junction in the opposite direction.
In the N-region where the electrons combine with the equal number of holes from the P-region, then from the negative terminal of battery the equal number of electrons enters the N-region and replace the electrons lost due to combination with holes near the junction. These electrons move towards the lift side of the junction and combine with new holes. This process allow the large current to flow.
2. Reverse based : The voltage potential is connected negative, (-ve) to the P- type material and positive, (+ve) to the N-type material across the diode which has the effect of Increasing the PN junction diode's width.
Vi characteristic of p-n junction diode:
When a diode is connected in a Forward Bias condition, a negative voltage is
applied to the N-type material and a positive voltage is applied to the P-type material. If this external voltage becomes greater than the value of the potential barrier, approx. 0.7 volts for silicon and 0.3 volts for germanium, the potential barriers opposition will be overcome and current will start to flow.
-- types of diode
1. Zener diode :
The diodes which operate on the principle of break down Voltage with damage produced by zener and of avalanche effects, are called zener diodes. It is heavily doped P-N junction diode which work in the reverse bias and operate in the break down region If reverse voltage of the diode is increased beyond its limit then two types of break downs are possible.
2. P-N junction diode
3. Tunnel diode
4. Varactor diode
5. Schottky diode
6. Photo diode : A photodiode is a p - n junction diode that consumes light energy to produce an electric current.
7. PIN diode
8. Laser diode
9. Avalanche diode
10. LED : It is a type of diode P-N junction diodes which produces glare when electrons are emitted on applying the proper forword bias across the diode. This diode has a property of giving light during recombination and at junction, it gives more light during forward biased. It has very long life .
The working voltage of light depending Resistor is just above 12 volt on forward biased and a series resistance is connected with the diode for its protection.
difference between photo diode and light emitting diode :
-- Photo diode : - it is work in reverse based
- it converter light energy in to band electrical light
-- Light emitting diode : - it is work in forward based
-
USES OF DIODE : Diodes can be used as Rectifiers, Signal limiters, Voltage Regulators,
Switches, signal modulators, signal mixers, signal demodulators, and oscillators. The fundamental property of a diode is its tendency to conduct electric current
in only one direction.
SOME IMPORTANT QUESTION AND ANSWER OD DIODE :
Q1. A crystal diode has ….………..
A. one pn junction
B. two pn junctions
C. three pn junctions
D. none of the above Ans=A
extra information:
- Crystal diode have one PN junction
- transistor have two PN junction
- U J T have one PN junction
- A C R have three PN junction
Q2. A crystal diode has forward resistance of the order of
A. ΚΩ
B. Ω
C. ΜΩ
D. none of the above Ans=B
extra information :
- forward Resistance of diode is low
- reverse resistance of diode is high
Q3. If the arrow of crystal diode symbol is positive w.r.t. bar, then dio
A. forward
B . reverse
C. either forward or reverse
D. none of the above Ans=A
Q4. The reverse current in a diode is of the order of
A. KA
B. MA
C. µA
D. A Ans=C
Q5. The forward voltage drop across a silicon diode is about
A. 2.5 V
B. 3 V
C. 10 V
D. 0.7 V Ans= D
extra information:
- for germanium diode 0.1 v to 0.3 v
Q6. A crystal diode is used as
A. an amplifier
B. a rectifier
C. an oscillator
D. a voltage regulator Ans=B
Q7 The d.c. resistance of a crystal diode is
A. the same as
B. more than
C.Tess than
D. none of the above Ans=C
Q8. An ideal crystal diode is one which behaves as a perfect... when forward based
A. conductor
B. insulator
C. resistance material
D. none of the above Ans=A
Q 9. The leakage current in a crystal diode is due to.......
A. minority carriers
B. majority carriers
C. junction capacitance
D. none of the above Ans=A
extra information:
- load current for majority
- leakage current for minority
Q10. If the temperature of a crystal diode increases, then leakage current
A. remains the same
B. decreases
C. increases
D. becomes zero Ans=C
Q11. The PIV rating of a crystal diode is .............. that of equivalent vacume diode
A. the same as
B. lower than
C. more than
D. none of the above Ans=C
extra information:
- PIV of Crystal diode is more
- PIV OF vacume diode is low
Q12. If the doping level of a crystal diode is increased, the breakdown voltage..
A. remains the same
B. is increased
C. is decreased
D. none of the above Ans=C
Q13. The knee voltage of a crystal diode is approximately equal to
A. applied voltage
B. breakdown voltage
C. forward voltage
D. barrier potential Ans=D
Q14. When the crystal current diode current is large, the bias is
A. forward
B. inverse
C. poor
D. reverse Ans= A
Q15. A crystal diode is a ................ device
A. non - linear
B. bilateral
C. linear
D. none of the above Ans=A
Q16. A crystal diode utilises..... characteristic for rectification
A. reverse
B. forward
C. forward or reverse
D. none of the above Ans=B
Q17. When a crystal diode is used as a rectifier, the most important consideration is....
A. forward characteristic
B. doping level
C. reverse characteristic
D. PIV rating Ans=D
Q18. If the doping level in a crystal diode is increased, the width of depletion layer.....
A. remains the same
B. is decreased
C. in increased
D. none of the above Ans=C
Q19. A zener diode has........
A. one pn junction
B . two pn junctions
C . three pn junctions
D . none of the above Ans=A
Q20. A zener diode is used as
A . amplifier
B. a voltage regulator
C . a rectifier
D. a multivibrator Ans=B
Q21. The doping level in a zener diode is................ that of a crystal diode
A. the same as
B. less than
C. more than
D. none of the above Ans=C
Q22. A zener diode is always.....
A. reverse
B. forward
C. either reverse or forward
D. none of the above Ans=A
.jpg "Connection of diode forward based and reverse based")
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