MEWAR UNIVERSITY

END TERM EXAMINATION- DECEMBER 2018

COURSE: B.TECH – BRANCH : EEE – SEMESTER : 3RD
PAPER NAME & CODE: Electronic Devices & Circuits ()

MAX MARKS: 85 TIME: 3:00 HRS

PART 1
Note: Attempt all Questions. All Question Carry one Marks.

1. In a semiconductor diode, the time constant equals to

(a) Value of majority carrier lifetime
(b) Value of minority carrier lifetime
(c) Diffusion capacitance time constant
(d) Zero

2. Normal biasing of transistor is

(a) Forward bias the Emitter-Base and reverse bias the Collector-Base
(b) Forward bias both the Emitter-Base and Collector-Base
(c) Reverse bias both the Emitter-Base and Collector-Base
(d) Reverse bias both Emitter-Base and forward bias the Collector-Base

3. A voltage regulator is based on the principle of

(a) Rectification
(b) Amplification
(c) Zener breakdown
(d) Avalanche breakdown
4. The intrinsic stand-off ratio of UJT is
(a) Always equal to zero
(b) Always equal to unity
(c) Always greater than unity
(d) Always less than unity

5. Avalanche breakdown occurs when

(a) The forward current is excessive
(b) The forward bias exceeds a certain value
(c) The reverse bias exceeds a certain value
(d) The potential barrier is reduced to zero

6. The β value of a transistor can be determined from the curve plotted between
(a) VB E and IE for constant VC E
(b) VB E and IC for constant VC E
(c) VC E and IE for constant IB
(d) VC E and IC for constant IB
7. The DC current gain of a transistor is
(a) Always positive and greater than unity
(b) Always positive and less than unity
(c) Always positive and equal to unity
(d) Always positive and equal to infinity

8. What is the type of capacitance effect exhibited by the PN junction, when it is

reverse biased?
(a) Transition capacitance
(b) Diffusion capacitance
(c) Space charge capacitance
(d) Drift capacitance

9. Which of the following statements are correct?

1. In semiconductor, the mobility of electrons is more than that of holes
2. In semiconductor, when temperature increases, the resistivity also increases
3. Metal has positive TCR
4. In metals, thermal conductivity is inversely
proportional to electrical conductivity at constant temperature
(a) 1, 2, 3 (b)1, 2, 4
(c) 2, 3, 4 (d)1, 3, 4

10. The Hall coefficient of an intrinsic semiconductor is

(a) Positive under all conditions
(b) Negative under all conditions
(c) Zero under all conditions
(d) Zero at 0°K
11. In intrinsic semiconductor
(a) The electron density is twice the hole density
(b) The electron density is thrice the hole density
(c) The electron density is square root of the hole density
(d) The electron density is same as the hole density

12. The color emitted by an LED depends mainly on

(a) Type of material used
(b) Type of biasing applied
(c) Recombination rate of charge carriers
(d) Environmental conditions

13. Consider the following statements

1. LED is also known as direct gap diode
2. LCD generates light
Of these statements
 (a) 1 is correct but 2 is wrong
(b) 2 is correct but 1 is wrong
(c) Both 1 & 2 are correct
(d) Both 1 & 2 are wrong

14. Which of the following statements is/are correct?

(a) Two discrete diodes connected back-to-back can work as a transistor
(b) Heat sink is a sheet of insulator used to dissipate the heat developed at the collector
junction of a power transistor
(c) The collector leakage current is strongly independent of temperature
(d) The collector junction of transistor is heavily doped

15. Electrostatic discharge may kill

(a) BJT
(b) FET
(c) UJT
(d) MOSFET

16. An electron in a completely filled band

(a) Contributes to the flow of electric current
(b) Does not contributes to the flow of electric current
(c) Can move but doesn’t contribute to the flow of electric current
(d) None of these

17. Consider the statements:

Statement I: Fermi level is slightly lowered by adding the donor impurity
Statement II: Fermi level is the maximum energy that any electron can have at room
temperature. Which of the following is correct?
(a) Statement I
(b) Statement II
(c) Both statements I & II
(d) Either statement I or II

18. Consider the statements given below

Statement I : In FET the generator current is proportional to the input voltage.
Statement II: In BJT, the generator current is proportional to the input current.
Which of the following is valid?
(a) Statement I
(b) Statement II
(c) Both statements I & II
(d) Either statement I or II

19. The device having closer characteristics with an ideal current source is
(a) Vacuum diode
(b) Zener diode
 (c) UJT
(d) Transistor in common base mode

20. Transistor is a
(a) Current controlled current device
(b) Current controlled voltage device
(c) Voltage controlled current device
(d) Voltage controlled voltage device

21. The JFET acts as a _______ along vertical parts of the drain curve.

(a) Resistor (b) Current source (c) Voltage source (d) Current sink

22. Photoluminescence which persists for some period after excitation is known as
(a) Phosphorescence
b) Tri-luminescence
(c) Fluorescence
(d) Bioluminescence

23. At 300ºK, the forbidden energy gap in silicon is

(a) 0.78 eV (b) 1.21 eV
(c) 0.72 eV (d) 1.10 eV

24. To improve the efficiency of an amplifier we have to --

    a) Reduce the power dissipation ratio.
    b) Reduce supply voltage.
    c) Reduce the load power.
    d) Reduce unwanted power loss.

25. The cascade amplifier is a multistage configuration of

a) CC-CB .b) CE-CB c) CB-CC d) CE-CC

26. The circuit shown is a

1
(A) low pass filter with f3dB = (R 1 + R 2)C rad/s
 1
(B) high pass filter with f3dB = rad/s
R1C
1
(C) low pass filter with f3dB = rad/s
R1C
1
(D) high pass filter with f3dB = (R 1 + R 2)C rad/s

27. The following circuit has a source voltage VS as shown in the graph. The
current through the circuit is also shown.

The element connected between a and b could be

28. The common emitter forward current gain of the transistor shown is βF = 100
 The transistor is operating in
(A) Saturation region (B) Cutoff region
(C) Reverse active region (D) Forward active region

29. The typical frequency response of a two-stage direct coupled voltage amplifier is as
shown in figure

30. Charge on the capacitor is

(a) directly related to voltage and inversely related to capacitance
(b) directly related to capacitance and inversely related to voltage
(c) directly related to both voltage and capacitance
(d) Inversely proportional to both voltage and capacitance

31._________ is an excellent device for interfacing digital IC’s to high power loads.
(a) Depletion mode power MOSFET
(b) Enhancement mode power MOSFET
(c) JFET
(d) Bipolar transistor

32.___________ indicates how effectively the input voltage controls the output current
in a JFET.
(a) Slow rate
(b) Transconductance
(c) Transresistance
(d) Intrinsic stand-off ratio

33. Which one of the following is a unique characteristic of Schottky transistor?

(a) Lower propagation delay
(b) Higher propagation delay
(c) Lower power dissipation
(d) Higher power dissipation

34. For a MOSFET the gate current

(a) Is decedent on drain current
(b) Increases with increase in drain voltage
(c) Decreases with decrease in drain voltage
(d) Is negligibly very small

35. Small signals refers to

(a) Low amplitude signals
(b) Low frequency signals
(c) Small signals as compared to bias currents
(d) Small signals as compared to bias currents & voltages in a circuit
 PART 2

Note: Attempt Five Questions and at least one question from each Section. All Question
Carry Equal Marks.

Section-A
1.
a) Define forbidden energy gap.
What is avalanche break down mechanism in Zener diode?
Define punch through mechanism in BJT.
List the applications of tunnel diode

2.
(a) Which is the most commonly used transistor configuration. Why?
(b) Draw the symbol for N-channel E-MOSFET.
(c) What is PIV in case of half wave and full wave rectifier?
(d) Define Thermal runaway.

Section-B

3.
(a) Compare CE, CB and CC configurations.
(b)(b) What is the effect of change in temperature on the stability of operating point?

4. For the fixed bias configuration of Fig., determine:

(1) (2) (3) (4) (5) (6) (7)

Fig.
 Section-C

5. Explain A FET amplifier in the common source configuration with a neat circuit
diagram.

6. i) Define Eber’s Moll model of a BJT.

ii)What is the relation between α and β in BJT?

iii) A certain transistor has a current gain of 0.99 in CB configuration. Calculate its current gain
in the CE configuration another transistor has β =80, determine it’s
α.

Section-D

7. a) Distinguish between JFET and MOSFET.

b) Draw the symbol for p- channel E-MOSFET.
c) Define pinch- off- voltage of JFET.

8. a) Compare between CS and CG in FET amplifier.

b) What are the applications of MOSFET?
c) What are the differences between BJT and JFET?

Section-E

9.
a) What is meant by Amplification and in what region of the characteristics the transistor is
operated as amplifier?
b) The output of common emitter amplifier is 1800 out of phase with the input. Explain
the
reason.

10.Explain RC coupled amplifier with circuit diagram, working and Frequency response of
signal.
 MEWAR UNIVERSITY
END TERM EXAMINATION- DECEMBER 2018
COURSE: B.TECH – BRANCH : EEE – SEMESTER : 3RD
PAPER NAME & CODE: Electronic Devices & Circuits ()

MAX MARKS: 85 TIME: 3:00 HRS

PART 1
Note: Attempt all Questions. All Question Carry one Marks.

1. An ideal diode can be considered as an

(a) Amplifier (b) Bi-stable switch
(c) Oscillator (d) Fuse

2. Zener diode exhibits

(a) Avalanche breakdown
(b) Zener breakdown
(c) Both (a) & (b)
(d) Neither (a) nor (b)
3. Avalanche breakdown occurs when
(a) The forward current is excessive
(b) The forward bias exceeds a certain value
(c) The reverse bias exceeds a certain value
(d) The potential barrier is reduced to zero
4. Doping is a process of
(a) Purifying semiconductor material
(b) Increasing impurity percentage
(c) Removal of foreign atoms
(d) Increasing the bias potential

5. Tunnel diode, with its negative resistance characteristics can be employed for
(a) Current amplification
(b) Voltage amplification
(c) Power amplification
(d) All of the above

6. UJT can be used as

(a) Oscillator
(b) Amplifier
(c) Oscillator and amplifier
(d) Either as oscillator or amplifier
7. The dynamic resistance of diode is
(a) Constant and independent of operating voltage
(b) Constant and dependent on operating voltage
(c) Not a constant and independent of operating voltage
(d) Not a constant and dependent on operating voltage

8. The turn-on time of a typical transistor is equal to

(a) Delay time

(b) Rise time
(c) Storage time
(d) Sum of delay time & rise time

9. A Schottky diode has

(a) Insulator - Semiconductor junction
(b) Semiconductor - Semiconductor junction
(c) Metal - Semiconductor junction
(d) Metal - Metal junction
10. Which is the largest transistor current?
(a) Emitter current
(b) Base current
(c) Collector current
(d) Both Emitter & Collector currents

11. Junction gate type of FET can be operated

(a) Only in depletion mode
(b) Only in enhancement mode
(c) Both depletion & enhancement modes
(d) Either depletion or enhancement mode

12. Typical UJT structure has

(a) Lightly doped N-type silicon bar with ohmic contacts at its each end
(b) Heavily doped N-type silicon bar with ohmic contacts at its each end
(c) Lightly doped P-type silicon bar with ohmic contacts at its each end
(d) Heavily doped P-type silicon bar with ohmic contacts at its each end

13. The symbol given below denotes

G
S

(a) n channel depletion MOSFET

 (b) p channel depletion MOSFET
(c) n channel enhancement MOSFET
(d) p channel enhancement MOSFET

14.Determine the invalid statement.

(a) For an n-channel JFET, both VGS and VP are negative
(b) For a p-channel JFET, both VGS and VP are posi-tive
(c) For an n-channel JFET, IDSS is positive
(d) For a p-channel JFET, IDSS is positive
15. Consider the statements
Statement I: N-channel MOS transistors are faster than p-channel MOS transistor.
Statement II: Surface field effect is the operational principle of MOSFETs.
Which of the above is/are a valid one?
(a) Statement I only
(b) Statement II only
(c) Both statements I and II
(d) Either statement I or II
16. N-P-N transistors are preferred ones than P-N-P transistors for digital application
because
(a) Electron mobility is more compared to holes mobility
(b) They are cheaper
(c) They are costlier
(d) Easy availability in the market
17. The gate voltage required for the conduction of an n-channel enhanced mode MOSFET
having a threshold voltage of 2V is
(a) 0 V (b) 1 V
(c) 2 V (d) More than 2 V
18. An N-type semiconductor as a whole is
(a) Positively charged
(b) Negatively charged
(c) Electrically neutral
(d) Can’t be defined
19.The main application of the enhancement mode MOSFET is
(a) Amplification
(b) Switching
(c) Tuning
(d) Rectification
20. The main advantage of cascade amplifier is
a. Low input resistance
b. Low input capacitance
c. High output resistance
d. High output capacitance
21. The base current of a transistor is typically
a. Less than emitter current
b. Greater than emitter current
 c. Same as emitter current
d. Equal to the sum of emitter and collector currents
22. The pinch-off voltage of JFET has a same magnitude as that of
a. Gate voltage
b. Gate source voltage
c. Drain–source voltage
d. None of these
23. The Hall angle of a metal sample is
a. Independent of the magnetic flux density B
b. Independent of the carrier mobility
c. Independent of the density of free carriers
d. Dependent on magnetic flux density
24. ICBO in a transistor can be reduced by
a. Reducing IB
b. Reducing VCC
c. Reducing IE
d. Reducing the temperature

25. A series RL circuit with R = 100 ohms, L = 50 Hz is supplied to a dc source of 100V.

The time taken for the current to rise 70% of its steady state value is
(a) 0.3 seconds (b) 0.6 seconds
(c) 0.9 seconds (d) 1.0 seconds

26. For an n-channel enhancement mode MOSFET, the drain current

(a) Decreases with increases in drain voltage
(b) Decreases with decrease in drain voltage
(c) Increases with increases in gate voltage
(d) Increases with decrease in gate voltage

27. When a phototransistor is reverse biased, is kept in dark condition, the current flowing
through the device corresponds to
a. Zero current
b. Reverse saturation current
c. Maximum flow of device current
d. Minimum flow of device current

28. The main use of class C amplifier –

a) As stereo amplifier. b) As distortion generator.
c) As an RF amplifier. d) In communication sound equipment.

29. The signal to be amplified is current signal and the output desired is a voltage signal.
Which of the following amplifier can perform this task?
a) Voltage amplifier
b) Current amplifier
c) Transconductance amplifier
d) Transresistance amplifier

30)   Why is the Darlington configuration not suitable for more than two transistors?

a. Because leakage current increases and voltage gain decreases with multiple number of transistors
b. Because leakage current decreases and voltage gain increases with multiple number of transistors
c. Because leakage current as well as voltage gain increases with multiple number of transistors
d. Because leakage current as well as voltage gain decreases with multiple number of transistors

31)   Consider the assertions given below. 

A. Replacement of each coupling and bypass capacitors by a short circuit

B. Replacement of transistor by its hybrid equivalent model for further analysis
C. Replacement of DC voltage sources by a short circuit

Which is the correct sequential order of steps to be carried out for analysis of a transistor amplifier
circuit?

a. A, B, C
b. B, A, C
c. A, C, B
d. C, A, B

32)   What should be the level of input resistance to allow the occurrence of source loading in
common base amplifier configuration?

a. Low
b. High
c. Moderate
d. Stable

33)   What is the phase-shift between input and output voltages of CE amplifier?

a. 90°
b. 120°
c. 180°
d. 270°

34)   Which capacitor is used to block DC portion by allowing to pass only AC portion of the
amplified signal to load?

a. Input Coupling Capacitor

b. Bypass Capacitor
c. Output Coupling Capacitor
d. All of the above
35. In an RC coupled amplifier, the voltage gain over mid-frequency range …………….
(a) Changes abruptly with frequency
(b) Is constant
(c) Changes uniformly with frequency
(d) None of the above

PART 2
Note: Attempt Five Questions and at least one question from each Section. All Question
Carry Equal Marks.

Section-A

1. Draw the Construction diagram and characteristics of the Photo diode.

2. What is a Tunnel diode? Explain the construction and working with neat band diagrams? Draw
its characteristics.
Section-B

3. Draw the drain characteristics of depletion mode MOSFET. Explain different operating regions.

4. Determine the dc level of and for the network of fig.

Fig.

Section-C

5. Explain the construction and working of CE configuration of BJT. also explain its input output
characteristics.

6.Write the ac equivalent circuit for voltage divider JFET configuration and determine Zi,
Z0 and Av.

Section-D
7. What is a Biased clipper? Explain the operation of a clipping circuit with the help of circuit
diagram and waveform.

8. Define h :.. _parameters. Draw the complete hybrid equivalent circuit of CE,CB,CC transistor.
 Section-E

9. Draw a circuit diagram for a transformer coupled amplifier and explain its working.

10. Define and explain the following terms:

(a) Decibel gain (b) Frequency response (c) Bandwidth

MEWAR UNIVERSITY
END TERM EXAMINATION- DECEMBER 2018
 COURSE: B.TECH – BRANCH : EEE – SEMESTER : 3RD
PAPER NAME & CODE: Electronic Devices & Circuits ()

MAX MARKS: 85 TIME: 3:00 HRS

PART 1
Note: Attempt all Questions. All Question Carry one Marks.

1. Which of the following doesn’t have forbidden energy gap between valence band and
conductor band?
a. Conductor
b. Insulator
c. Semiconductor
d. None of the above
2. Avalanche breakdown occurs when
a. The forward current is excessive
b. The forward bias exceeds a certain value
c. The reverse bias exceeds a certain value
d. The potential barrier is reduced to zero
3. Doping is a process of
a. Purifying semiconductor material
b. Increasing impurity percentage
c. Removal of foreign atoms
d. Increasing the bias potential
4. With reference to transistor which of the following is correct?
a. IC = IE + IB
b. IB = IC + IE
c. IE = IB + IC
d. IE = IB
5. Localized hot spots and device destruction can take place in power transistors due to
a. Avalanche breakdown
b. Primary breakdown
c. Second breakdown
d. Quasi-saturation breakdown
6. Consider the following statements regarding a semiconductor
1. Acceptor level lies close to valence band
2. Donor level lies close to valence band
3. N-type semiconductor behaves as a conductor at 0°K
4. P-type semiconductor behaves as an insulator at 0°K
(a) 1 & 2 are correct (b) 1 & 3 are correct
(c) 1 & 4 are correct (d) 2 & 3 are correct

7. The barrier potential of Schottky diode is

0.35
(a) 0.25 V (b) V
(c) 0.45 V (d) 0.56
 V
8. As the temperature is increased, the voltage across the diode carrying constant current
(a) Increases
(b) Decreases
(c) Remains constant
(d) Fluctuates between low and high threshold values
9. Current flow in the semiconductor slap is due to
a.Drift phenomenon
b. Diffusion phenomenon
c. Recombination phenomenon
d. All of the above
10. Which one is the valid statement with respect to PN junction diode?
a. Under forward bias, the electrons from P region & holes from N region drift towards the
junction

b. A junction diode cannot be used as a switch in electrical circuits

c. Depletion capacitance is voltage independent
d. Diffusion current of minority carriers is proportional to the concentration gradient
11. With reference to JFET configuration, match the following
Common Source
(P) (1) No phase shift
Configuration between input &
output
Common High input
(Q) Drain (2) imped-
ance & low
Configuration output
impedance
(R) Common Gate (3) Source follower
Configuration
(a) P-1, Q-2, R-3
(b) P-2, Q-3, R-1
(c) P-2, Q-1, R-3
(d) P-3, Q-1, R-2
12. The constant current area of FET lies between
(a) 0 & IDSS
(b) Cut off & Pinch off regions
(c) Cut off & Saturation regions
(d) Pinch-off & break-down regions
13. Typical UJT structure has
(a) Lightly doped N-type silicon bar with ohmic contacts at its each end
(b) Heavily doped N-type silicon bar with ohmic contacts at its each end
(c) Lightly doped P-type silicon bar with ohmic contacts at its each end
(d) Heavily doped P-type silicon bar with ohmic contacts at its each end
14. Which is valid with respect to JFET?
(a) Operated in depletion and enhancement modes
(b) Gate is not insulated from channel
(c) Channel doesn’t permanently exist
(d) It possesses low input impedance
15. Silicon & carbon have a
(a) Diamond cube (dc) structure
(b) Simple cube (sc) structure
(c) Face centered cube (fcc) structure
(d) Body centered cube (bcc) structure

16. Breakdown in a silicon UJT was observed to occur at a voltage of 6V, for a V BB = 10V
its stand off ratio is found to be
0.6
(a) 1.66 (b) 0
0.5
(c) 0.54 (d) 1
17. For a MOSFET the gate current
a.Is decedent on drain current
b. Increases with increase in drain voltage
c.Decreases with decrease in drain voltage
d. Is negligibly very small
18. When a transistor is turned from ON to OFF, the transistor comes to OFF state,
a.Once the input signal is removed
b. As soon as the input signal is reversed
c.As soon as the power supply is switched off
d. After the excess charge stored in the base region is removed.
19. FETs are used in an amplifier to obtain
(a) Low input impedance
(b) Low output impedance
(c) High input impedance
(d) High output impedance

20. The transconductance JFET at the Q-point is _________ the maximum

transconductance which occurs when Vds = 0.
a. Less than
b. Greater than
c. Equal to
d. None of the above
21. The current gain of a transistor is
a.The ratio of collector current to emitter current
b. The ratio of collector current to base current
c.The ratio of base current to collector current
d. The ratio of emitter current to collector current
22. The Hall angle of a metal sample is
(a) Independent of the magnetic flux density B
(b) Independent of the carrier mobility
(c) Independent of the density of free carriers
(d) Dependent on magnetic flux density
23. ICBO in a transistor can be reduced by
(a) Reducing IB
(b) Reducing VCC
(c) Reducing IE
(d) Reducing the temperature
24. The maximum operating frequency of a diode when used as a switch
a.Depends on the diode characteristics and switching voltages
b. Depends on switching voltages
c.Depends on diode characteristics
d. None of the above
25. If a transistor emitter current is 2mA, the collector current is
(a) Greater than 2 mA
(b) Less than 2 mA
(c) Equal to 2 mA
(d) Equal to 4 mA
26. A photodiode is used in reverse bias because
a.Majority of electron-hole pairs swept are reversed across the junction
b. Only one side is illuminated
c.Reverse current is small compared to photo-current
d. Reverse current is large compared to photocurrent
27. For an n-channel enhancement mode MOSFET, the drain current
a. Decreases with increases in drain voltage
b. Decreases with decrease in drain voltage
c. Increases with increases in gate voltage
d. Increases with decrease in gate voltage

28. FET has offset voltage of about

(a) 0.2 volts (b) 0.6 volts
(c) 1.0 volts (d) 3.6 volts
29. At 300ºK, the forbidden energy gap in germanium is
(a) 0.543 eV (b) 0.632 eV
(c) 0.72 eV (d) 0.89 eV

30. When a multistage amplifier is to amplify d.c. signal, then one must use …….. coupling
(a) RC
(b) Transformer
(c) Direct
(d) None of the above

31. ………….. coupling provides the maximum voltage gain

(a) RC
(b) Transformer
(c) Direct
(d) Impedance

32. In practice, voltage gain is expressed ……………

(a) In db
(b) In volts
(c) As a number
(d) None of the above

33. Transformer coupling provides high efficiency because …………

(a) Collector voltage is stepped up
(b) c. resistance is low
(c) collector voltage is stepped down
(d) none of the above

34. Transformer coupling is generally employed when load resistance is ………

(a) Large
(b) Very large
(c) Small
(d) None of the above

35. The final stage of a multistage amplifier uses ………………

(a) RC coupling
(b) Transformer coupling
(c) Direct coupling
(d) Impedance coupling

PART 2
 Note: Attempt Five Questions and at least one question from each Section. All Question
Carry Equal Marks.

Section-A

1.Explain semi-conductors, insulators and metals classification using energy band diagrams.

2. With circuit and necessary waveforms explain the operation of bridge rectifier.

Section-B

3. Write a short note on following topics:

(1) Bias Stabilization (2) Operating Point (3) Thermal Runway
4. Determine the dc bias voltage and the current For the voltage divider bias network
of fig.

Fig.

Section-C
5. Explain the operation of N-channel enhancement type MOSFET with the help of it’s (ID-VDS) and
(ID-VGS) characteristics.

6. (a)Define Ripple factor and derive expression for it for the following (i) Half wave rectifier
(ii) Full wave rectifier

(b) A FET has a drain current of 4 mA, if IDSS is 10 mA and VP is - 6V. Find the
value of Gate to Source voltage.

Section-D
7. Draw and explain the CB characteristics of a transistor.
8. (a) What are the advantages of CE amplifier?
(b) Compare JFET and MOSFET

Section-E

9. Write short notes on the following:

(1) Puss pull amplifier (2)Direct coupled amplifier

10. a) List the applications of UJT.

b) Explain the Diffusion and Drift currents for a semiconductor.