EC6202- ELECTRONIC DEVICES AND CIRCUITS
2 MARKS AND 16 MARKS (Q&A)
UNIT 1
1. Define PN junction.
When a p type semiconductor is joined to a N type semiconductor the contact surface is
called PN junction. P Type (majority of holes and minority of electrons) and N Type (majority of
electrons and minority of holes).
2. Explain the forward bias of diode (PN junction). (MAY 2014)
If p type terminal is connected to Anode (positive electrode), and N type terminal is
connected to cathode (Negative electrode) it is known as forward bias. At forward bias, large
current will flow in the range of milli amperes (10-3A). Forward bias is equivalent to short
circuit.
3. Explain reverse bias of diode (PN Junction).
If p type is connected to cathode and N type is connected to anode, it is reverse bias. At
reverse bias, small current will flow in the range of micro amperes (10-6). Reverse bias is
equivalent to open circuit.
4. Explain the V-I characteristics of PN Junction diode.
It is a graph drawn between voltage in x axis and current in y axis.
5. A Germanium diode has a saturation current of 10 μA at 300°K. Find the saturation
current at 400°K. (NOV 2012)
I300 = 10μA T1 = 300K T2 = 400K
I400 = I300 X 10-6 X 210 = 10.2 mA.
6. What is the effect of junction temperature on forward current and reverse current of a
PN diode?
For the same forward voltage, the forward current of a PN diode increases and reverse
saturation current increases with increase in junction temperature.
7. Differentiate between breakdown voltage and PIV of a PN diode.
The breakdown voltage of a PN diode is the reverse voltage applied to it at which the PN
junction breaks down with sudden rise in reverse current. Whereas, the peak inverse voltage
(PIV) is the maximum reverse voltage that can be applied to the PN junction without damage to
the junction.
,8. Define rectifier. (NOV 2013)
It is a device which converts alternating current into direct current.
9. Define knee voltage.
It is the forward voltage of a PN diode at which the current thorough the junction starts
increasing rapidly.
10. Define breakdown voltage.
It is the reverse voltage of a PN junction diode at which the junction breaks down with
sudden rise in the reverse current.
11. Mention the type of rectifier circuits. (MAY2015)
(i) Half wave rectifier
(ii) Full wave rectifier
(a) centre tap rectifier
(b) Bridge rectifier
12. Explain the Half wave circuit.
Half wave rectifier circuit consists of one Semiconductor Diode D1 and load Resistance
RL. That is current will flow during positive half cycle and no current will be conducted during
negative half cycle.
13. List the advantages of full bridge rectifier.
1. Centre-tapped transformer is not needed.
2. For the same secondary voltage, the output is doubled than that of the centre-tap circuit.
14. Define Zener diode.
A zener diode is a properly doped crystal diode which has a sharp breakdown voltage.
15. Compare between half wave and full wave rectifiers.
1. The efficiency of a full wave rectifier is double that of a half wave rectifier
2. The ripple factor is large and frequency of voltage is low in a half wave rectifier, hence the
waveform cannot be easily smoothed whereas in full wave rectifier, the frequency is large
therefore can be filtered easily with simple filtering circuits.
16. Define ripple factor
The ripple factor is a measure of purity of the dc output of a rectifier and is defined as
,17. Define rectifier efficiency.
The rectification efficiency tells us what percent of total input ac power is converted into
useful dc output power. Thus rectification efficiency is defined as
18. Define voltage regulation
Voltage regulation is a measure of the ability of a rectifier to maintain a specified output
voltage with the variation of load resistance and is defined as follows.
19. List the classification of filters
1. Low pass filter which transmits low frequencies to the load and attenuates high frequencies.
2. High pass filter which transmit high frequencies.
3. Band pass filter which transmits a band of frequencies.
20. Define LED. (NOV 2013)
The PN junction diode can emit light through a process known as electro luminescence. When a
diode is forward biased, majority of the carriers on both side of the junction will cross the
junction potential barrier. This recombination emission is responsible for the diode emitting
light.
21. Define LCD (Liquid Crystal Display). (MAY 2014)
A thin film of LC fluid is sandwiched between two glass plates. The glass plates are
coated with conductive transparent in the film formed of the desired alpha numeric image.
LCD’s consume less power and have the shortest life.
22. Mention the types of LCD.
Dynamic scattering
Field effect.
23. Mention the materials used in LED. (MAY 2014)
Gallium Arsenic Zinc Antimony.
Gallium Phosphorous.
GA As Ps.
Ga PN.
, 24. What is an ideal diode?
An ideal diode is one which offers zero resistance when forward biased and infinite
resistance when reverse biased.
25. Compare ideal diode as a switch.
An ideal diode when forward biased is equivalent a closed (ON) switch and when reverse
biased, it is equivalent to an open (OFF) switch.
26. Draw the circuit diagram of PN Diode
27. Draw the V-I characteristics of an ideal diode.
28. List the PN diode parameters. (MAY 2013)
1. Bulk Resistance. ( )
2. Static Resistance/Junction Resistance (or) DC Forward Resistance ( or )
3. Dynamic Resistance (or) AC Forward Resistance ( or or )
4. Reverse Resistance ( )
5. Knee Voltage ( )
6. Breakdown Voltage ( )
7. Reverse Current (or) Leakage Current
29. State the PN diode ratings.
2 MARKS AND 16 MARKS (Q&A)
UNIT 1
1. Define PN junction.
When a p type semiconductor is joined to a N type semiconductor the contact surface is
called PN junction. P Type (majority of holes and minority of electrons) and N Type (majority of
electrons and minority of holes).
2. Explain the forward bias of diode (PN junction). (MAY 2014)
If p type terminal is connected to Anode (positive electrode), and N type terminal is
connected to cathode (Negative electrode) it is known as forward bias. At forward bias, large
current will flow in the range of milli amperes (10-3A). Forward bias is equivalent to short
circuit.
3. Explain reverse bias of diode (PN Junction).
If p type is connected to cathode and N type is connected to anode, it is reverse bias. At
reverse bias, small current will flow in the range of micro amperes (10-6). Reverse bias is
equivalent to open circuit.
4. Explain the V-I characteristics of PN Junction diode.
It is a graph drawn between voltage in x axis and current in y axis.
5. A Germanium diode has a saturation current of 10 μA at 300°K. Find the saturation
current at 400°K. (NOV 2012)
I300 = 10μA T1 = 300K T2 = 400K
I400 = I300 X 10-6 X 210 = 10.2 mA.
6. What is the effect of junction temperature on forward current and reverse current of a
PN diode?
For the same forward voltage, the forward current of a PN diode increases and reverse
saturation current increases with increase in junction temperature.
7. Differentiate between breakdown voltage and PIV of a PN diode.
The breakdown voltage of a PN diode is the reverse voltage applied to it at which the PN
junction breaks down with sudden rise in reverse current. Whereas, the peak inverse voltage
(PIV) is the maximum reverse voltage that can be applied to the PN junction without damage to
the junction.
,8. Define rectifier. (NOV 2013)
It is a device which converts alternating current into direct current.
9. Define knee voltage.
It is the forward voltage of a PN diode at which the current thorough the junction starts
increasing rapidly.
10. Define breakdown voltage.
It is the reverse voltage of a PN junction diode at which the junction breaks down with
sudden rise in the reverse current.
11. Mention the type of rectifier circuits. (MAY2015)
(i) Half wave rectifier
(ii) Full wave rectifier
(a) centre tap rectifier
(b) Bridge rectifier
12. Explain the Half wave circuit.
Half wave rectifier circuit consists of one Semiconductor Diode D1 and load Resistance
RL. That is current will flow during positive half cycle and no current will be conducted during
negative half cycle.
13. List the advantages of full bridge rectifier.
1. Centre-tapped transformer is not needed.
2. For the same secondary voltage, the output is doubled than that of the centre-tap circuit.
14. Define Zener diode.
A zener diode is a properly doped crystal diode which has a sharp breakdown voltage.
15. Compare between half wave and full wave rectifiers.
1. The efficiency of a full wave rectifier is double that of a half wave rectifier
2. The ripple factor is large and frequency of voltage is low in a half wave rectifier, hence the
waveform cannot be easily smoothed whereas in full wave rectifier, the frequency is large
therefore can be filtered easily with simple filtering circuits.
16. Define ripple factor
The ripple factor is a measure of purity of the dc output of a rectifier and is defined as
,17. Define rectifier efficiency.
The rectification efficiency tells us what percent of total input ac power is converted into
useful dc output power. Thus rectification efficiency is defined as
18. Define voltage regulation
Voltage regulation is a measure of the ability of a rectifier to maintain a specified output
voltage with the variation of load resistance and is defined as follows.
19. List the classification of filters
1. Low pass filter which transmits low frequencies to the load and attenuates high frequencies.
2. High pass filter which transmit high frequencies.
3. Band pass filter which transmits a band of frequencies.
20. Define LED. (NOV 2013)
The PN junction diode can emit light through a process known as electro luminescence. When a
diode is forward biased, majority of the carriers on both side of the junction will cross the
junction potential barrier. This recombination emission is responsible for the diode emitting
light.
21. Define LCD (Liquid Crystal Display). (MAY 2014)
A thin film of LC fluid is sandwiched between two glass plates. The glass plates are
coated with conductive transparent in the film formed of the desired alpha numeric image.
LCD’s consume less power and have the shortest life.
22. Mention the types of LCD.
Dynamic scattering
Field effect.
23. Mention the materials used in LED. (MAY 2014)
Gallium Arsenic Zinc Antimony.
Gallium Phosphorous.
GA As Ps.
Ga PN.
, 24. What is an ideal diode?
An ideal diode is one which offers zero resistance when forward biased and infinite
resistance when reverse biased.
25. Compare ideal diode as a switch.
An ideal diode when forward biased is equivalent a closed (ON) switch and when reverse
biased, it is equivalent to an open (OFF) switch.
26. Draw the circuit diagram of PN Diode
27. Draw the V-I characteristics of an ideal diode.
28. List the PN diode parameters. (MAY 2013)
1. Bulk Resistance. ( )
2. Static Resistance/Junction Resistance (or) DC Forward Resistance ( or )
3. Dynamic Resistance (or) AC Forward Resistance ( or or )
4. Reverse Resistance ( )
5. Knee Voltage ( )
6. Breakdown Voltage ( )
7. Reverse Current (or) Leakage Current
29. State the PN diode ratings.
