test.1&sol

1

DO NOT OPEN THIS TEST BOOKLET UNTIL YOU ARE ASKED TO DO SO

Test Booklet Series

TEST BOOKLET

Electronics & Communication – Paper

Topic Test: EDC&Analog circuit

Time Allowed: One Hour

Maximum Marks: 100

INSTRUCTIONS

1. IMMEDIATELY AFTER THE COMMENCEMENT OF THE EXAMINATION YOU SHOULD

CHECK THAT THIS TEST BOOKLET DOES NOT HAVE ANY UNPRINTED OR TORN OR

MISSING PAGES OR ITEMS ETC. IF SO, GET IT REPLACED BY A COMPLETE TEST

BOOKLET.

2. ENCODE CLEARLY THE TEST BOOKLET SERIES A, B, C, OR D AS THE CASE MAY BE IN

THE APPROPRIATE PLACE IN THE ANSWER SHEET.

3. You have to enter your Roll Number on the

Test Booklet in the Box provided alongside.

DO NOT write anything else on the Test Booklet.

4. This Test Booklet contains 60 items (questions). Each item comprises four responses (answers). You

will select the response which you want to mark on the Answer Sheet. In case you feel that there is

more than one correct response, mark the response which you consider the best. In any case, choose

ONLY ONE response for each item.

5. You have to mark all you responses ONLY on the separate Answer Sheet provided. See directions in

the Answer Sheet.

6. All items carry equal marks.

7. Before you proceed to mark in the Answer Sheet the response to various items in the Test Booklet,

you have to fill in some particulars in the Answer Sheet as per instructions sent to you with your

Admission Certificate.

8. After you have completed filling in all your responses on the Answer Sheet and the examination has

concluded, you should hand over to the Invigilator only the Answer Sheet. You are permitted to take

away with you the Test Booklet.

9. Sheets for rough work are appended in the Test Booklet at the end.

10. Penalty for wrong answers:

THERE WILL BE PENALTY FOR WRONG ANSWERS MARKED BY A CANDIDATE IN THE

OBJECTIVE TYPE QUESTION PAPERS.

(i) There are four alternatives for the answer to every question. For each question for which a

wrong answer has been given by the candidate, one-third (0.33) of the marks assigned to that

question will be deducted as penalty.

(ii) If a candidate gives more than one answer, it will be treated as a wrong answer even if one

of the given answers happens to be correct and there will be same penalty as above to that

question.

(iii) If a question is left blank, i.e., no answer is given by the candidate, there will be no penalty

for that question

DO NOT OPEN THIS TEST BOOKLET UNTIL YOU ARE ASKED TO DO SO

2

Q.1. The mobility of electrons in a semiconductor decrease with increasing donor density because:

1. Doping decreases the relaxation time of electrons

2. More holes are generated so that the effective mobility decreases

3. Electrons are trapped by the donors

Which of the following statements are correct:

(A) Only 1 (B) Only 3 (C) Both 1 & 2 (D) 1, 2 & 3

Q.2. Consider the following statements:

Electrical conductivity of a metal has negative temperature coefficient since

1. electron concentration decreases with temperature.

2. electron mobility decreases with temperature.

3. electron-lattice scattering decreases with temperature.

Which of the statements given above are correct ?

(A) Only 1 (B) Only 2 (C) Both 1 and 2 (D) 1, 2 & 3

Q.3. Consider the following statement : A heavily doped semiconductor has

1. Negative temperature coefficient of resistance

2. Negative temperature coefficient of conductance

3. Positive temperature coefficient of resistance

4. Positive temperature coefficient of conductance


(A) 1 & 2 (B) 2 & 3 (C) 1 & 4 (D) 3 & 4

Q.4. Mobility of electrons is higher than mobility of holes because:

1. Curvature of CB is smoother than VB

2. Effective mass of electrons is lower than that of holes

3. Effective mass of electrons is higher than that of holes

4. Curvature of VB is smoother than CB


(A) 1 & 2 (B) 2 & 3 (C) 1 & 3 (D) 3 & 4

Q.5. Consider the following statements about temperature effect in Ge and Si:

1. Si is more stable for temperature than Ge

2. Si is less sensitive towards temperature than Ge.

Which of the statements given above are correct ?

(A) Only 1 (B) Only 2 (C) Both 1 and 2 (D) Neither 1 nor 2

Q.6. Consider the following statements for an n-type semiconductor:

1. Donor level ionization decreases with temperature.

2. Donor level ionization increases with temperature.

3. Donor level ionization is independent of temperature.

4. Donor level ionization increases as ED (donor energy level) moves towards the conduction band at

a given temperature.

Which of these statements is / are correct?

(A) 1 only (B) 2 only (C) 2 and 4 (D) 3 only

3

Q.7. Excess carriers are generated in a sample of N-type semiconductor by shining light at one end. The

current flow in the sample will be made up of

(A) Diffusion flow of carriers (B) drift flow of carriers

(C) Both diffusion and drift flow of carriers (D) Neither diffusion nor drift flow of carriers

Q. 8. The majority carriers in an N-type& P-type semiconductor have an average drift velocity v in a

direction perpendicular to a uniform magnetic field B. The electric field E induced due to Hall effect

acts in the direction:

(A) v × B in both N type and P type (B) B × v in both N type and P type

(C) v × B in N type only (D) v is parallel to B in both N type and P type

Q.9. A half-effect transducer with Hall coefficient KH = –1 × 10–8

is required to measure a magnetic field

of 10,000 gauss. A 2 mm bismuth slab is used as the transducer with a current of 3A. The output

voltage of the transducer will be

(A) –7.5 × 10–6

V (B) –15 × 10–6

V (C) –20 × 10–4

V (D) –22.5 × 10–4

V

Q.10. A si wafer is doped with 1015

Phosphorous atoms/cm3.what is the position of Fermi-level of EF at

room temperature :

(A) Above intrinsic level by an amount of 0.3 eV (B) Above intrinsic level by an amount of 0.6 eV

(C) Below intrinsic level by an amount of 0.3 eV (D) Below intrinsic level by an amount of 0.6 eV

Q.11. If the reverse voltage across a P-N Junction is increased three times then the junction capacitance:

(A) will decrease by a factor of 2 (B) will decrease by a factor of 3

(C) will increase by a factor of 2 (D) will increase by a factor of 3

Q.12. Consider the following statements about P-N Junction:

1. Forward biasing of P-N junction decreases the value of drift current

2. Reverse biasing of P-N junction increases the value of drift current

3. An unbiased P-N Junction develops a built-in potential at the junction with the N-side positive and

the P-side negative.

4. The unbiased p-n junction behaves as a battery and supplies current to a resistance connected

across its terminals.


(A) 1, 2 & 3 (B) 2, 3 & 4 (C) 3 & 4 (D) 1, 2, 3 & 4

Q.13. Consider the following statement about reverse current of a Silicon& Germanium diode:

(A) Reverse current in both Ge and Si is independent of reverse bias voltage

(B) Reverse current in Ge only is independent of reverse bias voltage

(C) Reverse current in Si only is independent of reverse bias voltage

(D) Reverse current in both Ge and Si does not depend upon temperature

Q.14. The i-v characteristics of the diode in the circuit given below are

0.7A, 0.7V

i 500

0 A, 0.7V

4

The current in the circuit is

(A) 10mA (B) 9.3mA (C) 6.67mA (D) 6.2mA

Q.15. A semiconductor has a band gap of 0.62eV.Find the maximum wavelength for resistance change in

the material by photon absorption.

(A) 1 µm (B) 1.5 µm (C) 2.0 µm (D) 2.5 µm

Q.16. An LED is made of GaAsP having a band gap of 1.9eV. what is the color of the radiation emitted

from light:

(A) Blue (B) Green (C) Yellow (D) Red

Q.17. Which of the following statements are true for a semiconductor that is used as a photo conductor ?

1. It should have doping either N type or P type

2. It should have small response time.

3. It should have an energy band gap value that matches with frequency of light that is used to excite

the photoconductor.

4. Its dark conductivity is small.

Select the correct answer using the codes given below :

(A) 1, 2 & 3 (B) 2, 3 & 4 (C) 1, 3 & 4 (D) 1, 2, 3 & 4

Q.18. The reverse bias breakdown of high speed silicon transistors is due to

(A) Avalanche breakdown mechanism at both the junctions

(B) Zener breakdown mechanism at both the junctions

(C) Zener breakdown mechanism at base-collector junction and avalanche breakdown mechanism at

base-emitter junction

(D) Zener breakdown mechanism at base-emitter junction and avalanche breakdown mechanism at

base-collector junction

Q.19. Find the correct match between Group-I and Group-II

Group-I Group-II

E- Varactor diode 1. Voltage reference

F- PIN diode 2. High frequency switch

G- Zener diode 3. Tuned circuits

H- Schottky diode 4. Current controlled attenuator

(A) E-4, F-2, G-1, H-3 (B) E-2, F-4, G-1, H-3

(C) E-3, F-4, G-1, H-2 (D) E-1, F-3, G-2, H-4

Q.20. Consider the following statements about conditions that make a metal-semiconductor contact

rectifying:

1. N-type semiconductor with its work function s, greater than the work function M of the metal.

2. N-type semiconductor with its work function s, smaller than the work function M of the metal.

5

E B C

WE WB WC

3. P-type semiconductor with its work function s, greater than the work function M of the metal.

4. P-type semiconductor with its work function s, smaller than the work function M of the metal.

(A) 1 and 3 are correct (B) 2 and 3 are correct

(C) 1 and 4 are correct (D) 2 and 4 are correct

Q.21. These are the different methods followed to take p – n – p – n device form its conducting state to the

non-conducting state?

1. Reducing the anode current below the holding value.

2. By changing the polarity of anode voltage

3. Reducing the gate current to zero

4. Reducing the gate voltage to zero

5. By changing the polarity of gate voltage

Which of the following statements are correct?

(A) Only 1 & 2 (B) 1, 2 & 3 (C) 1, 3, & 5 (D) 1, 2, 3, 4 & 5

Q.22. Consider the following statements :

1. A UJT is a voltage controlled device

2. A SCR is Current controlled device


(A) Only 1 (B) Only 2 (C) Both 1 & 2 (D) Neither 1 nor 2

Q.23. Moor law relates to

(A) speed of operation of bipolar devices (B) speed of operation of MOS device

(C) power rating of MOS devices (D) level of integration of MOS devices

Q.24. Consider the following statements used for high speed transistor:

1. Thin base width

2. Heavy doping in base region

3. Non uniform doping in base region


(A) 1 & 2 (B) 2 & 3 (C) 1 & 3 (D) 1, 2 & 3

Q.25. In a bipolar junction transistor. The collector break down voltage increases :

(A) the base doping is increased and the base width is reduced

(B) the base doping is reduced and the base width is increased

(C) the base doping base and width are reduced

(D) the base doping and base width are increased

Q.26. Which of the B.J.T is best suited for analog circuitry (for amplification purpose)

Base width = WB

Collector width is = WC

Emitter width = WE (Device is p-n-p type)

p minority carrier lifetime in base

t transit time of minority carrier in base

6

+10V

V =3VBB

+

–

p n p

WB

(A) B C EW W W (B) B E CW W W

p t p t

(C) B E CW W W (D) B E CW W W

t p t p

Q.27. A PNPN diode is biased in forward blocking region with an anode to cathode voltage of 36 Volt. If

1 20.25, 0.35 and leakage currents are 160 nA then the forward resistance of diode is given by:

(A) 45 M (B) 50 M (C) 80 M (D) 120 M

Q.28. In the circuit shown below, the silicon npn transistor Q has a very high value of . The required

value of R2 in k to produce CI 1mA is

(A) 20 (B) 30 (C) 40 (D) 50

Q.29.

The trans-conductance gm of the transistor used in the CE amplifier shown in the above circuit,

operating at room temperature is

(A) 92 mA/V (B) 46 mA/V (C) 184 mA/V (D) 25 mA/V

Q.30. For a given B.J.T shown:

If we manage to increase the WB (width) (Base width) to twice of its initial value then β (gain factor)

of the device

(A) Increase to 2 twice of its initial value (B) decreases to 1

2 its initial value

(C) Increase to 4 times of its initial value (D) decreases to 1

4 its initial value

7

Q.31. Which of the following are essentials of a transistor biasing circuit?

1. Proper zero signal collector current flow

2. VCE should not fall below 0.5 V for Germanium and 1 V for Silicon

3. Ensure stabilization of operating point

4. Loading to the source

(A) 1, 2 and 3 only (B) 1, 2 and 4 only (C) 3 and 4 only (D) 1, 2, 3 and 4

Q.32. A MOS capacitor made using N type substrate is in the accumulation mode. The dominant charge in

the channel is due to the presence of:

(A) Holes (B) Electrons

(C) Positively charged ions (D) Negatively charged ions

Q.33. MOSFET is a switch preferred at high frequency in digital circuit because:

(A) Fabrication of MOSFET is simpler (B) Minority carriers are absent in MOSFET

(C) It is a symmetrical device (D) It has very high input impedance

Q.34. Consider the following statements about channel length modulation in MOSFET:

1. Length of channel decreases due to decrease in drain voltage

2. Length of channel decreases due to increase in drain voltage

3. This effect decreases output impedance

4. This effect increases output impedance

Which of the following statements are true:

(A) 1 & 3 (B) 2 & 3 (C) 1 & 4 (D) 2 & 4

Q.35. An N-channel JFET has IDSS=2mA and VP=-4 volt its transconductance gm( in milli-ohm) for an

applied gate to source voltage VGS=-2 Volt is.

(A) 0.25 (B) 0.5 (C) 0.75 (D) 1.0

Q.36. Consider the following statements about Threshold voltage of MOSFET:

1. It should have value between (0.5V-3.0V)

2. This should have maximum value

3. Body effect changes the value of threshold voltage


(A) 1 & 2 (B) 2 & 3 (C) 1 & 3 (D) 1, 2 & 3

Q.37. Thermal runaway is not possible in FET because, as the temperature of FET increases

(A) the drain current increases (B) the mobility increases

(C) the mobility decreases (D) the transconductance increases

Q.38. Two MOSFETS M1 and M2 have channel widths and lengths of W, L and 2W, L/2 and drain currents

of I1 and I2 respectively. Assuming that both M1 and M2 are ON, under the same temperatures and

biasing voltages, which one of the following is true??

(A) 12

4

II (B) 1

22

II (C) I2 = 2I1 (D) I2 = 4I1

Q.39. What is the output impedance of a source follower, if a large value of resistance Rs is connected b/w

source and ground. (If rd = )

(A) Rs (B) 1/gm (C) Rs + 1/gm (D) gm

8

I + –VD1

D2

1006v

Q.40. The circuit shown in Figure, best describes as a :

(A) Clamper circuit (B) Slicer circuit or 2 – level clipper

(C) Full wave voltage doubler (D) Base clipping circuit or bottom – clipper

Q.41. In an energy band-diagram of an open circuited P-N, Junction diode, the energy band of N-region

has shifted relative to that of a P-region. (Where V0 is contact potential)

(A) Downward by V0 (B) Downward by qV0

(C) Upward by V0 (D) Upward by qV0

Q.42. In a rectifier circuit if an a.c. supply is 60 Hz, then what is the a.c. ripple at output?

(A) It will be 60 Hz for Half wave rectifier and 60 Hz for Full wave rectifier

(B) It will be 60 Hz for Half wave rectifier and 120 Hz for Full wave rectifier

(C) It will be 120 Hz for Half wave rectifier and 60 Hz for Full wave rectifier

(D) It will be 120 Hz for Half wave rectifier and 120 Hz for Full wave rectifier

Q.43. In the given circuit, D1 is an ideal germanium diode and D2 is a silicon diode having its cut-in

voltage as 0.7 V, forward resistance as 20 Ω and reverse saturation current (Is) as 10 nA.

What are the values of I and V for this circuit respectively?

(A) 60 mA and 0 V (B) 50 mA and 0 V (C) 53 mA and 0.7 V (D) 44 mA and 1.58 V

Q.44. If a BJT is operating in active region with IC= 1mA and β=100 then what is the value of r

(A) 1.5 Kohm (B) 2.0 Kohm (C) 2.5 Kohm (D) 3.0 Kohm

Q.45. A CE-amplifier has RL = 10 kΩ. Given hie = 1 kΩ, hfe = 50, hre = 0 and 1/hoe 40 kΩ. What is the

voltage gain?

(A) –500 (B) –400 (C) –50 (D) –40


1. CE configuration is suitable at high/Radio frequency due to presence of Junction capacitances

2. CB Configuration is suitable for low/audio frequency


(A) Only 1 (B) Only 2 (C) Both 1 & 2 (D) Neither 1 nor 2

Q.47. If an amplifier has power of 1 watt then what is its value in dBm:

(A) 10dBm (B) 15dBm (C) 20dBm (D) 30dBm

9

•

•

Vout

vi

Vbias

•Iout

M2

M1

Q.48. Consider the following statements about lower cut off frequency in BJT:

1. It is mainly decided by coupling capacitor

2. Phase shift in single stage at lower 3dB is 225 degree

3. Phase shift in single stage at lower 3dB is 135 degree


(A) Only 1 (B) Only 2 (C) 1 & 2 (D) 1 & 3

Q.49. Two identical stages with each having a voltage gain of 50,input resistance of 1Kohm and output

resistance of 250 ohm are cascaded then what is the open circuited voltage gain of combined

amplifier:

(A) 1000 (B) 1500 (C) 2000 (D) 2500

Q.50. Consider the following statements about cascoded amplifier :

1. It has large voltage gain and high output impedance

2. It is wide band amplifier and is used for high frequency applications

3. It has high value of current gain

(A) 1 & 2 (B) 2 & 3 (C) 1 & 3 (D) 1, 2 & 3

Q.51. Two identical NMOS transistors M1 and M2 are connected as shown below. Vbias is chosen so that

both transistors are in saturation. The equivalent gm of the pair is defined to be out

i

I

V

at constant Vout.

The equivalent gm of the pair is:

(A) The sum of individual gm’s of the transistors (B) The product of individual gm’s of the transistors

(C) Nearly equal to the gm of M1 (D) nearly equal to gm/go of M2

Q.52. As NPN transistor has a beta cut off frequency fβ of 1 MHz and common emitter short circuit low

frequency current gain β of 200.I fits unity gain frequency fT and the alpha cut-off frequency fα

respectively are:

(A) 200 MHz, 201 MHz (B) 200 MHz,199 MHz

(C) 199 MHz, 200 MHz (D) 201 MHz,200 MHz

Q.53. In a voltage-voltage feedback as shown below, which one of the following statements is TRUE about

type of feedback:

(A) Series-Series

(B) Series-Shunt

(C) Shunt-series

(D) Shunt-shunt

10

74 8

3

62 15

555

+5v

RA

RB

C CF

o/p

100K

v0

ix

10K

1M

vx

Q.54. Consider the following:

1. Oscillator 2. Emitter follower

3. Cascaded amplifier 4. Power amplifier

Which of these use feedback amplifiers?

(A) 1 and 2 (B) 1 and 3 (C) 2 and 4 (D) 3 and 4

Q.55. The function of the diode D in the timer circuit shown below is to

(A) Increase the charging time of C (B) Decrease the charging time of C

(C) Increase the discharging time of C (D) Decreases the discharging time of C

Q.56. In case of video amplifier wide banding is done by:

(A) Peaking coils only in series (B) Peaking coils only in shunt

(C) Peaking coils either in series or shunt (D) By use of neutralizing capacitors


1. Stagger tuning is used for wider band pass

2. Synchronous tuning is used for narrower band pass

3. In stagger tuning both tuned circuits are tuned to different frequency

4. In synchronous tuning both tuned circuits are tuned to same frequency


(A) 1, 2 & 3 (B) 2, 3 & 4 (C) 1, 3 & 4 (D) 1, 2, 3 & 4

Q.58. What is the value of i/p impedance Rin = (vx/ix) of circuit shown.

(A) 100 K (B) – 100 K (C) + 1 M (D) – 1 M

11

+

–

C

R

R L

Vi

V0

–

+C

R

v0

–

+

R1

R2

R3

C

Q.59. The OPAMP circuit shown in figure represents

(A) Low Pass Filter

(B) High Pass Filter

(C) Band Pass Filter

(D) Band Reject Filter

Q.60. Given circuit is used as a:

(A) Square wave generator (B) Sinusoidal wave generator

(C) Triangular wave generator (D) Monostable multivibrator

12

Engineering Service Examination -2014

SI No.

Electronics&Telecommunication Engineering

PAPER-EDC& Analog

(Conventional)

Time allotted: 90 Minute Maximum marks: 100

INSTRUCTIONS

Candidates should attempt Question No. 1 which is compulsory and remaining FOUR from questions taking

two each from section-A and Section-B. The number of marks carried by each question is indicated at the

end of the question. Answers must be written only in English. Assume suitable data if found necessary and

indicate the same clearly. Values of the following constants may be used wherever necessary:

Electronic charge = –1.6 × 10–9

Coulomb

Free space permeability = 4 × 10–7

Henry /m.

Free space permittivity = 9110

36

Farad/m.

Velocity of light in free space = 3 × 108 m/ sec.

Boltzmann constant = 1.38 × 10–23

joule /K.

Planck constant = 6.626 × 10–34

joule-sec.

Important: Candidates are to note that all parts and sub parts of a question are to be attempted

continuously in answer book. That is all parts and sub parts of a question being attempted must be

completed before attempting the next question.

Any page left blank in answer book must be clearly struck out. Answers that follow pages left blank

may not be given credit.

13

–

+

R1

v1

R

R1

C

v0+

–

VBE

+IB–

+5V

VBB

RB

ICBO

RL

I =0E

+

–VCC

Q.1. (a) (i) why Si is preferred over Ge in semiconductor physics? (3)

(ii) why mobility of electrons is higher than mobility of holes. (2)

(b) Explain variation of mobility with respect to temperature. (5)

(c) Explain channel width modulation and Body effect in case of MOS. (5)

(d) Derive the transfer function of the circuit shown below and identify the function of the circuit.(5)

SECTION-A

Q.2. (a) Explain Hall effect for N-type with Proper mathematical equations what is Hall coefficient for N

type semiconductor. (10)

(b) A silicon abrupt p-n junction at 300 K has acceptor density, Na = 1018

cm–3

and donor density,

Nd = 1015

cm–3

. If the intrinsic concentration, Ni = 1.5 × 1010

cm–3

, calculate the built-in voltage,

V0 Derive the relations used. (10)

Q.3. (a) In the transistor circuit shown below ICBO = 2 Amp at 25ºC and doubles for every 10º C

increase in temperature.

(i) Find maximum allowable value of RB if the transistor is to remain cut off at 75ºC. Assume

VBE(cut off) = – 0.1 V. (10)

(ii) If VBB = 1.0V and RB = 50 k how high may the temperature increase before the transistor

comes out of cut off ? (5)

(b) Explain Transfer characteristics of N Channel MOS. (5)

Q.4. (a) Draw the electrical equivalent circuit of a Quartz Crystal explaining the significance of the

various components of the circuit. (10)

(b) Draw neat sketches of Impedance vs Frequency, Reactance Versus Frequency of the Quartz

resonator indicating the critical frequencies and their values. (10)

14

+–

V0+

–

+

V1

V2

+

–

R1

R1

R2

R2

SECTION-B

Q.5. (i) Explain why bias stabilization is done in a bipolar junction transistor amplifier circuit. (5)

(ii) Draw a fixed bias circuit and a self bias circuit using a BJT and mention typical component

values and supply voltages for your circuit. (5)

(iii) Briefly explain the principle of operation of fixed bias and self bias circuits using BJT. (5)

(iv) Compare the relative merits and demerits of fixed bias and self bias circuits using BJT. from the

application point of view. Choose, with suitable reasons, the one which you would recommend

for cascaded amplifier operation. (5)

Q.6. (a) Explain the distinguishing features of astable, monostable and bistable multivibrator and give the

operational details of any one of them. (15)

(b) What are various type of wide banding techniques. (5)

Q.7. (a) Find the output voltage in terms of V1’ V2’ R1’ and R2 for the differential input amplifier

consisting of a base amplifier of infinite gain as show in the figure below. (10)

(b) Explain working of Wein bridge oscillator by use of OP-AMP circuit (10)

15

CB

VB

CB

VB

ED

IES 2014 Test-1 Solution:

1. (A) By increasing doping relaxation time is decreased because if more heavy material is doped

higher is the probability of collision and more carriers will collide with an ion in given time

& mean free time between collision is reduced so value of *

e&

m

so mobility value

will be reduced.

2. (B) In case of metal if temperature is () the number of electrons per unit volume will remain

same. Thermal speed will () and amplitude of atomic vibration will () due to that time

between successive collisions will decrease which will decrease mobility and conductivity

value will decreases.

3. (B) In case of heavily doped semiconductor, donor level is not in discrete form due to high value

of doping. In this case energy due to temperature will ignite internal interaction within ions

which will result in () in mobility & finally decrease in conductivity.

So with () in temp

ve

ve

R ve

G ve

4. (A) *

e

m

n p

* *

n pm m

V. B have attractive force from nucleus & internal force from near by electrons so that

curvature of CB is smooth than valance band & due to this reason effective man of e is less

than effective mass of hole.

5. (A) Si :14 2,8,4

Ge:32 2,8,18,4

In case of Silicon Valance electrons are tightly attached while in Germanium these electrons

are loosely attached so for same value of temperature Silicon is more temperature stable than

Germanium. If in case of Ge by 1ºC rise in temp conductivity will () around 5% and in Si it

is () around 7.5%.

6. (C) As statement (2) and statement (4) is true.

16

v

I+ + ++ + +

P-typefmZ

X

E

Y

7. (A) Diffusion flow of minority carrier.

8. (B)

m x x z z x z yF e B e B e v a B a ev B a

E B v

Because electric field direction is (+ay)

9. (B) H

B.IV

.W

H

ne

1 1K

ne

4

6HH 3

K BI 10 10 3V 15 10 V

w 2 10

10. (A) dF Fi

i

NE E KT n

n

11. (A) 2

1

R 01

2 R 0

V VC

C V V

1

2j R 0C V V

12. (C) Reverse current is independent of biasing in general.

13. (B)

0 v

i

0

I recomb in neutral region qn e

I recomb in dopletion region 2kT

In case of Ge reverse current is independent of Reverse bias but in Si it depends upon rev bias.

In both Ge and Si reverse current is temperature sensitive.

14. (D) 10 v v 0.7

i1000 500

15. (C)

16. (D) G

12375E (eV)

Å

12375

Å 6526Åor 652nm1.9

625 – 740 nm Red

565 – 595 nm Yellow

17

P N P

B

CE

Metal n-type

Metal

qXs

EC

EFS

Semi-conductor

520 – 565 nm Green

434 – 500 nm Blue

17. (B) Photoconductor material should always be intrinsic.

For a photoconductor material should be always intrinsic so that there will be significant

change in the value of conductivity. Response time should be fast and dark conductivity is

also small.

18. (D) Zener occurs at less than 6 V and avalanche breakdown occurs > 6 V.

19. (C)

20. (B) Metal – SC diode :– metal and n-type semi-conductor

Here n-type will be +ve & metal will be –ve.

No depletion layer formation, no current due to metal to semi-conductor here delay due to

recombination is absent.

Since e plunge into metal with high energy so this is known as hot carrier diode.

It has in this case cut in voltage is smaller than normal diode & reverse current due to

thermionic is higher.

It works like ohmic contact & rectifying contact. If conduction is equal in both the direction

then it is k/a ohmic otherwise rectifying.

N-type :

(1) Ohmic m s s mor

(2) Rectifying s m

P-type :

(1) Ohmic s m

(2) Rectifying s m

Heavily doped semiconductor will behave like ohmic and lightly will behave as rectifying.

21. (A) Once SCR is on then gate looses its control & can not be off until anode polarity is changed

or anode current is reduced below holding value.

22. (B) UJT is a current controlled device.

23. (D) Level of integration of MOS device

18

ia

ig

K

P

N

P

N

K

A

G

24. (C) H

t

1f

2

If heavy doping occurs then value of Hf will () so base should be lightly doped.

Due to non-uniform doping there will be external electric field which will support transit of

holes. Hence Hf will ().

25. (D) 2DB A D B

A

qNV N N W

2 N

AN collector doping

DN base doping

B base width

26. (B) WB must be minimum for higher amplification while Wc must be maximum so that there is

heat dissipation at the collector

27. (A)

1 2g CO CO

a

1 2

I I Ii

1

gI 0

1 2

9CO CO

a

1 2

I I 230 10i

1 1 0.6

9800 10 A 0.8 A

636R 10

0.8

R 45M

28. (C) Approximation method is used because value of is high

2B

2

R .3V 0.7 1 0.5 1.2V

R 60

29. (A) cm

T

Ig

V

30. (D)

2

p

2

B

2L

2

B

1

31. (A) There is no need of loading of source.

32. (B) N-type substrate means P-Channel MOSFET. In accumulation mode no channel formation there.

33. (B) Due to absent in minority carriers switch has high speed.

34. (B) When VDS is kept 0, and GSV 0 , channel remains flat. If value of DSV is then depletion

layer will penetrate into n-region & channel will get tapered which will further by

19

qVo

ECN

EVN

T

(f)

T

(f) (2f)

increasing the drain voltage. This problem can be solved by substrate voltage or body

voltage. This is channel length modulation.

35. (B) DSS GSm

p p

2I Vg 1

v v

36. (C) Threshold voltage should have minimum value.

37. (C) In case of FET value of ID () with () in temp due to two reasons.

If temp is () then mobility of concentration carrier will decreased and at the same time by

() temp, depletion region of both p and n junction becomes narrow

38. (D) 2

D GS TI k V V

Where n ox

Wk C

2L

1 1 2

2 1 2

I W L

I L W

1 1

1 1

L W

2L 2W

1

4

39. (C) 0 d s

m

1z V || R ||

g

if dV

s 0

m

1R ; z

g

40. (C)

41. (B)

42. (B)

43. (A)

44. (C) Cm

mT

Ir , g

g V

20

A1 A2

RiRo

45. (B) fei

oe L

hA

1 h R

if oe Lh R 0.1

i fe

oe L

A h

10h R 0.25

40

i

50A 40

11 10

40

i ie re i L ieR h h A R h 1k

i Lv

i

A R 40 10A 400

R 1

46. (D) CE has miller capacitance effect which limits its efficiency while CB does not have miller’s

capacitance hence suitable for high frequency.

47. (D)

48. (C) ov

L

AA

f1 j

f

at Lf f 45º 180 = 225º

49. (C) 11 2

1 0

RA A

R R

1000

25001250

= 2000

50. (A)

51. (C)

52. (A) T fe fef h f &f (1 h ) f

53. (B) Voltage – Series Series Shunt

Current – Series Series – Series

Voltage – Shunt Shunt Series

Current – Shunt Shunt – Shunt

54. (A) Oscillator has positive feedback and emitter follower has voltage series negative feed back

55. (D)

56. (C)

57. (D) In synchronous, both tuned amplifier is at same frequency & net b.w is ().

While in staggered, both ampr. has different frequency & resultant has higher B.W.

58. (B)

59. (A)

60. (C)

test.1&sol

Documents

complete test booklet

separate answer sheet

correct response

wrong answers

given answers

responses answers

following statements

mobility of electrons