EDC

Takshshila Institute of Engineering & Technology Department of Electronics and Communication

EDC (CS-304)- NON- GRADING

Page 1 of 25 Prof.D.K.singh

2012

QUIZ - I

Multiple Choice Questions

1. The PIN diode is used as

(a) rectifier (b) voltage controlled attenuator (c) amplifier

2. The diode used for a power limitter is

(a) signal diode (b) Zener diode (c) PIN diode (d) power diode

3. Most suitable diode for a phase shifter is

(a) power diode (b) avalanche diode (c) PIN diode

4. The PIN diode is used as

(a) square wave modulator (b) triangular wave modulator (c) sine wave modulator

5. No moving part is associated with the change in capacitance of

(a) gang capacitor (b) trimmer (c) varicap

6. The diode which permits remote tuning, is

(a) power diode (b) Varactor (c) Zener diode

7. The Zener effect is valid

(a) below 5 V (b) above 5 V (c) equal to 5 V (d) none of the above

8. The avalanche effect is valid

(a) below 5 V (b) above 5 V (c) equal to 5 V (d) none of these

9. The electron-hole pairs are generated in

(a) Zener mechanism (b) avalanche mechanism (c) none of the two

10. The diode which is preferred for dc coupling is

(a) signal diode (b) power diode (c) LED (d) Zener diode

11. Power diodes are used in




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(a) rectifier (b) amplifier (c) mixer

12. The power diodes are made of

(a) silicon (b) germanium (c) aluminium

13. Signal diodes are called

(a) general-purpose diodes (b) special purpose diodes (c) high power diodes

14. The PIN diode works as rectifier at

(a) low frequency (b) high frequency (c) all frequencies

15. The PIN diode has

(a) an intrinsic layer between heavily doped p and n-layers

(b) an n-layer between heavily doped p and n-layers

(c) and an p-layer between heavily doped p and n-layers

16. The Schottky diode turns OFF

(a) faster w.r.t p-n junction (b) slower w.r.t. p-n junction

(c) at the same speed as p-n junction

17. The minority carrier storage time in the Schottky diode is

(a) infinite (b) zero (c) 0.15 ms

18. Very close to the ideal diode is

(a) Zener diode (b) signal diode (c) Schottky diode




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Questions for Practice

1. Discuss the role of emitter, base and collector regions in the operation of BJT

2. Why is the base width very thin?

3. For normal operation how the base emitter and base collector junctions are biased?

4. Draw block diagrams of n-p-n and P-N-P transistors with batteries

5. What is ? How it is related with transistor currents?

6. What is the typical value of ?

7. How transistor and are related?

8. What is the typical value of ?

9. What is collector reverse saturation current? What is the cause of it?

10. What carrier makes up the largest component of current inside p-n-p and n-p-n

transistors?

11. What are the three possible configurations of BJT?

12. What is the meaning of symbols ICEO and ICBO?

13. What is the relation between ICO and ICEO?

14. Where do you bias transistor? Why do you bias it?

15. How can you justify neglecting VBE in fixed bias circuit but not in self-bias circuit?

16. What is 'fixed' in the fixed biased circuit?

17. How does the fixed bias circuit biases the base emitter junction and collector base

junction?

18. What is thermal runaway?

19. How does self bias circuit achieve thermal stability?




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20. How is a DC load line plotted on the output characteristic of BJT?

21. Draw the output characteristics of an n-p-n transistor in CE configuration and indicate the

active, cut-off, and saturation regions.

22. Discuss briefly the charge transport mechanism in a BJT.

23. Derive an expression for the terminal currents in a p-n-p transistor

24. Define and of a transistor and deduce the relationship between them. Find the

expression for the collector current IC in terms of the base current IB the reverse

saturation current ICO and .

25. A Ge transistor with = 0.98 gives ICO = 12 A when used in the CB configuration.

Obtain IC when the transistor is used in CE configuration with IB = 0.2 mA

26. Why transistor action cannot be achieved by connecting two diodes back to back?




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QUIZ - II


1. Current amplification factor in CB configuration is

(a) (b) 1 + (c) 1/(1 + ) (d)

2. Current amplification factor in CE configuration is

(a) (b) 1 + (c) 1/ (d)

3. Current amplification factor in CC configuration is

(a) (b) 1 + (c) 1/ (d)

4. Leakage current in CB configuration is

(a) ICBO (b) IBCO (c) ICEO (d) IECO

5. Leakage current in CE configuration is

(a) IC (b) ICBO (c) ICEO (d) ICB

6. ICEO and ICO are related as

(a) ICEO = ( + 1)ICO (b) ICEO = ICBO (c) ICEO < ICBO

7. The value of is

(a) unity(b) very near to unity(c) greater than unity(d) very much less than unity.

8. is related to as

(a) = /(1 + ) (b) = /(1 ) (c) = 1/(1 + )

(b) is related to as

(a) = /(1 + a) (b) = /(1 ) (c) = (1 )/

9. Which one is correct

(a) IE = IB + IC (b) IC = IB + IE (c) IE < (IB + IC)

10. Collector current and reverse saturation collector current are related as




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(a) IC > ICEO (b) IC < ICEO (c) ICO = ICEO

11. Which is correct

(a) IB < IC < IE (b) IE < IB < IE (c) IB = IC = IE

12. The arrow in a transistor terminal represents

(a) emitter (b) collector (c) base

13. The arrow in a transistor represents

(a) the direction of conventional current

(b) the opposite direction of conventional current

(c) the direction of flow of electrons

14. The doping level of emitter region is

(a) greater than collector and base region

(b) less than collector and base regions

(c) less than base but greater than collector region

15. The physical dimension of collector region is

(a) largest w.r.t the other two

(b) smallest w.r.t the other two

(c) equal to the rest of the two

(d) smaller than emitter but bigger than base

16. For normal amplifier operation

(a) EB junction is forward and CB junction is reverse biased

(b) EB junction is reverse biased and CB junction forward biased

(c) both are forward biased




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17. CB transistor has

(a) lower input and higher output resistances

(b) higher input and lower output resistances

(c) low input and output resistances

18. CE transistor has



(c) medium input and output resistances

19. CC transistor has



(c) low input and output resistances

20. The phase difference between the input and output currents in CB configuration are

(a) 180 (b) 0 (c) 90 (d) 45

21. The phase difference between the input and output current in CC configuration are

(a) 180 (b) 0 (c) 90 (d) 30

22. ICBO is

(a) collector to base current when emitter is open

(b) collector to base current when base is grounded

(c) collector to base current when base is connected to a resistance

23. ICEO flows in

(a) collector and emitter leads

(b) collector and base leads

(c) emitter and base leads




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24. In p-n-p transistor the emitter current flows

(a) out of emitter lead

(b) into emitter lead

(c) neither out nor in the emitter lead

25. In a BJT the

(a) base region is sandwiched between emitter and collector

(b) emitter region is sandwiched between base and collector

(c) collector is sandwiched between base and emitter

26. The quiescent state of transistor is when

(a) biased but no signal is applied

(b) it is unbiased

(c) no current flows

27. Maximum swing of signals occurs when Q-point along load line is selected at

(a) middle of the output characteristic

(b) the saturation point

(c) the cutoff point

28. The emitter efficiency of a junction transistor decreases with

(a) decrease of emitter doping

(b) increase of emitter doping

(c) decrease of base width

(d) decrease of base doping




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1. Explain operation of a MOSFET and its use as an amplifier.

2. Draw the h.f. equivalent circuit of a MOSFET and explain the significance of the different

elements of the circuit.

3. With the help of suitable band diagrams, distinguish between conditions of accumulation,

depletion and inversion in relation to a MOS structure. What is the condition of strong

inversion?

4. What is meant by static and dynamic RAM? Sketch the circuits of (a) a MOS inverter and

(b) a 1-bit memory cell using MOSFETs and explain how they operate.




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QUIZ - III


1. The main types of field effect transistors are

(a) UJT and FET (b) BJT and FET (c) JFET and MOSFET

2. The input impedance of the field effect transistor is

(a) very low w.r.t. BJT (b) very high w.r.t. BJT (c) medium w.r.t. BJT

3. The field effect transistor is an

(a) unipolar device (b) bipolar device (c) none of the above

4. The doping of substrate is

(a) high w.r.t. the source or drain

(b) low w.r.t. the source or drain

(c) moderate w.r.t. the source or drain

5. The n-channel field effect transistor has

(a) p-type substrate (b) n-type substrate (c) no substrate

6. The polarity of the gate w.r.t. the source in n-channel JFET is

(a) positive (b) negative (c) neutral

7. The charge carriers in an n-channel JFET are

(a) electrons (b) holes (c) protons (d) neutrons

8. The drain current of the n-channel JFET increases with

(a) increasing positive voltage at the gate

(b) decreasing positive voltage at the gate

(c) constant voltage at the gate




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9. The JFET are normally used in

(a) Ohmic region(b) saturation region(c) cut-off region

10. The parameters of JFET are related as

(a) gm = rd/ (b) gm = /rd (c) gm = rd

11. The input resistance of MOSFET is of the order of

(a) 100 M (b) 10 (c) 1 K

12. The field effect transistors are

(a) voltage controlled device(b) current controlled device

(c) neither current nor voltage controlled device

13. The field effect transistor offer

(a) low degree of isolation between input and output

(b) high degree of isolation between input and output

(c) complete short circuit between input and output

14. The field effect transistor is

(a) less noisy w.r.t. BJT (b) more noisy w.r.t. BJT

15. For quiet reception the front end of FM tuner contains

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

16. The gain-bandwidth of the field effect transistor is

(a) high w.r.t. BJT (b) low w.r.t. BJT (c) equal to the BJT

17. The IDSS of the FET is

(a) independent of pinch off voltage (b) dependent on pinch off voltage

18. At pinch-off, the drain current becomes

(a) zero (b) infinite (c) constant




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19. The high frequency gain of the FET is mainly limited by

(a) Cgs (b) Cds (c) Cgd

20. In an FET

(a) both junctions are forward biased

(b) both junctions are reverse biased

(c) one junction forward biased and the other reverse biased

21. When the reverse bias between the gate and the source increases, the pinch-off voltage

will become

(a) more

(b) less

(c) remains unaffected

22. For an amplifier, the FET is operated in

(a) VVR region (b) pinch-off region (c) avalanche breakdown region

23. If the reverse bias in a FET is increased, its gm will

(a) increase (b) decrease (c) not be affected (d) suddenly falls to zero

24. The minimum value of VDS to operate in the pinch-off region with Vpo = 4 V, IDSS = 8

mA, and VGS = 3 V is

(a) 4 V (b) 1 V (c) 4 V (d) 7 V

(Hint: VDS = VGS VPO = 3 V (4 V) =1 V)

25. The Vpo of an n-channel JFET with ND = 1016/cm3, r = 16, o = 8.854 10

14 F/cm, a =

0.5 m is

(a) 1.5 V (b) 1.4 V (c) 5 V (d) 0

26. The rd(ON) of an n-channel JFET with parameters in prob. 29 alongwith L = 20 m, Z =

103 m, n = 0.13 m2/Vs is

(a) 1 K (b) 961 K (c) 0.931 K (d) 0.0961 K




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27. The IDSS of an n-channel JFET with ND = 1022/m, a = 0.5 m, L = 20 m, z = 103m, n =

0.13 m2/Vs, Vpo = 5 V, is

(a) 10.4 mA (b) 100.4 mA (c) 1.04 mA(d) 0.104 mA

28. In a MOSFET, a low threshold voltage can be achieved by

(a) using the gate dielectric of lower dielectric constant

(b) increasing the substrate concentration

(c) decreasing the substrate concentration

(d) using a thick gate oxide.

29. In a MOSFET the threshold voltage can be lowered by

(a) increasing the gateoxide thickness

(b) reducing the substrate concentration

(c) increasing the substrate concentration

(d) using the dielectric of lower constant.

30. JFETs are normally used in

(a) Ohmic region (b) saturation region (c) cut-off region (d) breakdown region.

31. For values of drain voltage smaller than gate voltage, a MOSFET acts as a voltage

controlled

(a) current source (b) resistor (c) voltage source (d) capacitor.


1. Why is the bias stabilization required in transistor amplifiers? What are the various bias

stabilization methods? Draw the circuits and discuss their relative advantages and

disadvantages.

2. Draw fixed bias and a self-bias circuit for CE configuration. Discuss the operation of each

circuit and hence, explain which circuit gives better stability.




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QUIZ IV


1. The maximum output swing can be obtained when the Q-point is

(a) near saturation point (b) near cut-off point (c) in the middle of the load line

2. What value of stability factor should be selected?

(a) infinity (b) zero (c) finite

3. For good stability the Q-point should

(a) vary (b) fixed (c) none of these

4. The positive peak of the signal will be clipped off if the Q-point shifts towards

(a) cut-off (b) saturation (c) active regions

5. The voltage divider bias is used to make the Q-point

(a) independent of (b) independent of VBE (c) dependent of

6. Most popular bias arrangement is

(a) fixed base bias (b) collector to base bias (c) voltage divider bias

7. Improper biasing leads to

(a) distortion in output (b) distortion in input (c) heavy loading

8. For an amplifier junctions of BJT should be biased as

(a) base-emitter and base-collector both reverse biased

(b) base-emitter forward and base-collector reverse biased

(c) base-emitter and base-collector both forward biased

9. The stability factor lies in between

(a) zero and unity

(b) unity and (1 + )




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(c) (1 + ) and infinity

10. The best Q-point in an amplifier for faithful reproduction of the signal is selected

(a) near cut-off

(b) near saturation

(c) in the middle of the active region

11. With increasing value of the stability factor, the Q-point

(a) becomes poor

(b) becomes better

(c) is not affected

12. The thermal stability of fixed base bias circuit is

(a) poor

(b) good

(c) best

13. In the saturation region of the BJT

(a) VCE = VCC

(b) VCE 0

(c) VCE = 5V

14. The bypass capacitor across the emitter resistance

(a) increases the emitter current

(b) increases the output signal

(c) improves the stability factor

15. The stability factor S = + 1 is in the case of

(a) fixed base bias

(b) (b) collector to base bias




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(c) fixed base bias with emitter resistance

16. The stability factor of collector to base bias is better

(a) w.r.t. the fixed base bias

(b) (b) collector to base bias with emitter resistance

(c) self bias

17. Inclusion of an emitter resistance in any type of biasing circuit

(a) improves stability factor

(b) (b) worsens stability factor

(c) does not change stability factor


1. Draw the small signal low frequency model of a BJT in CE configuration. Using this

configuration, derive expression for the voltage gain of an emitter follower amplifier.

2. Derive an expression for the voltage gain in the CE transistor amplifier in terms of h-

parameters.

3. Why the value of R3 in bootstrapped amplifier cannot be more than few hundred ohm?

Justify it.

4. Show that the voltage gain of the bootstrapped amplifier is essentially unity.




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QUIZ V


1. The relationship between input and output voltage of a common emitter amplifier is

(a) always unity

(b) always positive

(c) always negative

(d) less than unity

2. The voltage gain of a common collector amplifier is

(a) always equal

(b) always positive

(c) always negative

3. The voltage gain of a common base amplifier is

(a) less than unity

(b) always positive

(c) always negative

4. The output current in a Class-C amplifier flows for

(a) full cycle

(b) more than half cycle

(c) less than half cycle

(d) half cycle

5. In Class-AB amplifier the output current flows for

(a) full cycle





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(d) half cycle

6. In Class-A amplifier the output current flows for

(a) full cycle



(d) half cycle

7. Voltage gain of CB amplifier configuration has phase shift of

(a) 180

(b) 90

(c) 360

(d) 45

8. The h-parameters of a BJT are

(a) dependent on RL

(b) dependent on ICQ

(c) independent of ICQ

(d) constant

9. The dimension of all the four h-parameters of a BJT are

(a) the same

(b) different

(c) none of these

10. The typical value of h-parameters of a BJT are

(a) hie = 1 K, hfe = 100, hre = 10 104, hoe = 10 10

6S

(b) hie = 10 K, hfe = 100, hre = 10 104, hoe = 10 10

6S




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(c) hie = 1 K, hfe = 100, hre = 10 104, hoe = 1010

6S

(d) hie = 100 K, hfe = 100, hre = 10 104, hoe = 10 10

6S

11. In an amplifier the output varies

(a) linearly for any amount of input amplitude

(b) linearly for restricted range of input amplitude

(c) nonlinearly for any amount of input amplitude

12. The h-parameters of a BJT are called

(a) small signal parameters

(b) large signal parameters

(c) T-parameters

(d) Z-parameter

13. The h-parameters of a BJT at high frequency

(a) remains constant

(b) varies with frequency

(c) none of these

14. The configuration that offers highest input resistance is

(a) CE

(b) CB

(c) CC

15. The amplifier that offers highest input resistance and the lowest output resistance

(a) CE

(b) CB

(c) CC




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16. The configuration that offers highest current amplification ratio but lowest voltage

amplification is

(a) CE

(b) CB

(c) CC

17. The configuration that offers highest power gain is

(a) CE

(b) CB

(c) CC

18. The important considerations in cascading of different configurations of BJT amplifier is

(a) matching of impedances

(b) matching of current gain

(c) matching of loads

19. The most popular general purpose amplifier configuration is

(a) CC

(b) CE

(c) CC

20. The CE amplifier configuration is preferred over others because it offers

(a) highest current gain, voltage, and power gains

(b) medium current gain, voltage, and power gains

(c) lowest current gain, voltage, and power gains

21. The input resistance of a CC configuration is 100 K with its load of 1 K, the hfe of the

BJT is approximately

(a) 500




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(b) 100

(c) 50

22. The configuration that behaves as a constant current source is

(a) CB

(b) CE

(c) CC

23. The two stage CC amplifier configuration provides approximately

(a) unity voltage gain

(b) 50 voltage gain

(c) none of these

24. The input voltage connected across the input of a CC stage is 50. Its output voltage

would be

(a) 5360

(b) 5180

(c) 50

(d) none of these

25. The buffer stage can employ the configuration

(a) CB

(b) CE

(c) CC

26. The stage which avoids loading the previous stage is called buffer amplifier. What is the

other name?

(a) CB

(b) CE




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(c) CC

27. The prime importance in designing a circuit is voltage amplification. Which configuration

is preferred for such case

(a) CB

(b) CB

(c) CC

28. The gain-bandwidth of an amplifier is

(a) always constant

(b) always variable

(c) none of these

29. The gain of an amplifier reduces by a factor of 10, the bandwidth

(a) remains constant

(b) increased by the same factor

(c) decreased by the same factor

(d) none of the above

30. The upper 3dB frequency of n-identical cascaded stages is

(a)

(b)

(c) nf2

31. (d) The upper 3dB frequency of a single stage amplifier is 1 MHZ, how many identical

stages will result in approximately 510 kHz upper 3 dB frequency.

(a) 2

(b) 33

(c) 4




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(d) 10

32. The upper 3 dB frequency of a single stage amplifier is 1MHz, what will be the 3 dB

frequency of ten identical cascaded stages

(a) 0.1 MHz

(b) 100 kHz

(c) 268 kHz

(d) 168 kHz

33. The effective bandwidth of indentically cascaded stages

(a) decreases

(b) very low

(c) none of the above

34. The bandwidth of an amplifier is approximately

(a) proportional to its upper 3 dB frequency

(b) inversely proportional to its upper 3 dB frequency

(c) product of its 3 dB frequencies

35. The rise time tr for a square wave input of an amplifier is related to its 3 dB frequency in

case of square wave input as

(a) tr = 0.35/f2

(b) tr = 0.90/f2

(c)

(d)

36. The bootstrap amplifier is associated with

(a) high input impedance

(b) low input impedance




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(c) none of these

37. The Darlington pair is characterized with

(a) very large output impedance

(b) very large input impedance

(c) very low input resistance

38. The output impedance of the Darlington pair amplifier is

(a) very large

(b) very low

(c) none of the above

39. The current gain of a Darlington pair is approximately

(a) / (1 + )

(b)

(c) 2

40. At half power frequencies, an amplifier voltage gain is lowered by

(a) 6 dB

(b) 3 dB

(c) 2 dB

(d) 0.5 dB

41. Compared to a CB amplifier, the CE amplifier has

(a) lower input resistance

(b) lower current amplification

(c) higher output resistance

(d) higher current amplification

42. One of the effects of negative feedback in amplifier is to




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(a) increase the noise

(b) decrease the bandwidth

(c) increase the harmonic distortion

(d) decrease the harmonic distortion

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