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M V G R COLLEGE OF ENGINEERING
DEPARTMENT OF ECE
EDC- Unit Wise Questions
Academic Year: 2011-12
Class: II BTech I Sem
Faculty: K. SARITHA RAJ
Branch: ECE
______________________________________________________________________________
UNIT – 1: Electron Ballistics and Applications
1.
What are the main parts of the CRT? Explain briefly with neat sketch.
[16]
2.
In a parallel plate diode, the cathode and anode are spaced 5mm apart and the
anode is kept at 200V d.c. with respect to cathode. Calculate the velocity and the
distance travelled by an electron after a time of 0.5ns, when
[16]
(a) The initial velocity of an electron is zero and
(b) The initial velocity is 2×106 m/s in the direction towards the anode.
3.
Two plane parallel plates A and B are placed 3 mm apart and potential of b is
made 200 V positive with respect to plate A. An electron starts from rest from
plate A. Calculate
(a) The velocity of the electron on reaching plate B.
(b) Time taken by the electron to travel from plate A to plate B, and
(c) Kinetic energy of the electron on reaching the plate B.
[16]
4.
An infinitely large parallel plane plates are spaced 0.8 cm apart. The voltage on
one of the plates is raised from 0 to 5 V in 1 ns at a uniform rate with respect to the
other. After this duration, the potential difference between the plates is suddenly
dropped to 0 V and remains the same thereafter. Find
(a) The position of the electron, which started with zero initial velocity from the
negative plate, when the potential difference drops to zero volt,
(b) The total time of transit of the electron from the cathode to the anode.
[16]
5.
Derive the expression for the deflection in an electrostatic deflection system. Hence
obtain the expression for electro static deflection sensitivity.
[16]
6.
What are the front panel controls of CRO? Explain.
[16]
7.
8.
Analyze the motion of an electron under perpendicular electric and magnetic fields.
[16]
(a) What is deflection Defocusing? Give the reasons of defocusing.
(b) Compare: Electrostatic deflection and magnetic deflection
(c) An electron beam is deflected of 10o degrees when it traverses in uniform
magnetic field, 3 cm wide, having a density of 0.6 mT. Calculate:
i. The speed of the electrons and
ii. The force on each electron. The direction of the beam is normal to that
of the flux.
[4+6+6]
9.
A charged particle having charge thrice that of an electron and mass twice that of an
electron is accelerated through a potential difference of 50 V before it enters a uniform
magnetic field of flux density of 0.02 Wb/m2 at an angle of 25o with the field. Find
(a) The velocity of the charged particle before entering the field,
(b) Radius of the helical path, and
(c) Time of one revolution.
[16]
10.
In a cathode ray tube having electric deflection system, the deflection plates are 2
cm long and have uniform spacing of 4mm between them. The fluorescent screen is 25
cm away from the centre of the deflection plates. Calculate the deflection sensitivity,
if the potential of the final anode is:
(a) 1000 V,
(b) 2000 V and
(c) 35000 V.
[16]
11.
Two parallel plates are kept a distance 12 cm apart. One plate is 800 V positive with
respect to the other. An electron starts from rest from the negative plate. Find the distance
travelled. Time taken and the kinetic energy of the electron when it has acquired a speed
of 5 × 106 m/s, at this instant, the potential across the plates is suddenly removed. Find
the total time of travel of the electron from the negative plate to the positive plate. [16]
12.
Derive the expression for the deflection in a magnetic deflection system. Hence
obtain the expression for magnetic deflection sensitivity.
13.
[16]
(a) In a CRO, the distance of the screen from the centre of the magnetic field is 20cm.
The deflecting magnetic field of flux density 1 × 10−4 Wb/M2 extends for a length of 2
cm along the tube axis. The final anode voltage in 800V.Calculate the deflection of the
spot.
(b) The electron beam in a CRT is displaced vertically by a magnetic field of flux density
2 × 10−4 Wb/m2. the length of the magnetic field along the tube axis is the same as that
of the electrostatic deflection plates. The final anode voltage is 800 V. Calculate the
voltage which should be applied to the Y - deflection plates 1 cm apart, to return the spot
back to the centre of the screen.
[6+10]
UNIT – 2: Review of Semi Conductor Physics
1.
2.
(a) Explain about semiconductor, Insulator & Conductor with neat sketch.
(b) State the Einstein relationship for semiconductor.
(c) State Pauli’s exclusion principle.
[6+5+5]
(a) Define law of junction.
(b) Explain the Fermi’s level in intrinsic semiconductor.
[6+10]
(a) Explain the Fermi level in extrinsic semiconductor.
(b) Write any four applications of PN diode.
[12+4]
4.
Explain the construction & Working principle of LCD.
[16]
5.
Explain drift & diffusion current in detail. Also write the expression for total current. [16]
6.
(a) Compare Tunnel diode & Conventional PN Diode.
(b) Write any four applications of Tunnel diode.
3.
[10+6]
UNIT – 3: Junction Diode Characteristics and Special Diodes
1.
(a) Short notes on LED voltage drop and current.
(b) Write short notes on Multi colour LED.
2.
Explain in detail PN junction energy band diagram of a PN diode.
3.
(a) Explain the volt ampere characteristics of PN diode.
(b) Explain the temperature dependence of VI characteristics.
[10+6]
[16]
[8+8]
4.
Explain in detail about the capacitance effect of PN junction diode in reverse biased
condition also derive the expression for that capacitance.
[16]
5.
(a) Define Mass Action Law.
(b) Explain N type & P type Semiconductors.
[4+12]
6.
(a) What is diffusion length (L)?
(b) A Diode operating at 300 k at a forward voltage of 0.4V carries a current of 10ma
when voltage is changed to 0.42V the current becomes thrice. Calculate the value of
reverse leakage current and η for the diode (Assume VT = 26 mv).
[4+12]
7.
Derive the diode current equation for the PN diode.
[16]
UNIT – 4: Rectifiers and Filters
1.
(a) Draw the circuit diagram of HWR. Explain its working. What is the frequency
of ripple in its output?
(b) A HWR circuit supplies 100mA d.c to a 250Ω load. Find the d.c output
voltage, PIV rating of a diode and the r.m.s. voltage for the transformer
supplying the rectifier.
[8+8]
2.
A voltage of 200Cos ωt is applied to HWR with load resistance of 5 K Ω. find the
maximum d.c current component, r.m.s. current, ripple factor, TUF and rectifier
efficiency.
[16]
3.
Derive the ripple factor of capacitor filter.
[16]
4.
(a) Describe transistor shunt regulator.
(b) Calculate the output voltage and zener current in the regulator circuit shown
in Figure 4.1
[6+10]
Figure 4.1
5.
Determine:
(a) DC output voltage,
(b) PIV,
(c) Rectification efficiency of the given circuit figure 4.2.
[16]
Figure 4.2
6.
Draw the circuit diagram of a FWR:
(a) With centre tap connection and
(b) Bridge connection and explain its operation.
[16]
7.
Derive all the necessary parameters of centre tapped FWR.
[16]
8.
(a) Why do we need filters in a power supply under what condition we shall prefer
a capacitor filter?
(b) Draw the block diagram of RPS.
(c) What is the function of a bleeder resistor?
(d) Describe the terms capacitor input filter and inductor input filter.
[5+2+5+4]
9.
(a) Compare : HWR, center tapped FWR & Bridge rectifier.
(b) A transformer with 20V r.m.s., 50Hz secondary, supplies a bridge rectifier having a
load of 200 . Determine the d.c output voltage, d.c load current and PIV rating of the
diode.
[6+10]
10.
Derive the ripple factor of Inductor filter.
[16]
11.
Derive all the necessary parameters of bridge rectifier.
[16]
12.
Derive the ripple factor of π- Filter with neat sketch.
[16]
UNIT – 5: Transistor
1.
Derive an Eber’s Moll equation for a transistor.
2.
Explain the input and output characteristics of common base transistor configuration.
[16]
3.
Derive the analytical expression for transistor characteristics.
[16]
4.
(a) Write the reason why the Ico value is negative for PNP transistor & Ico value
is positive for PNP transistor.
(b) Define base spreading resistance.
[10+6]
5.
6.
7.
[16]
(a) Write short notes on Emitter efficiency.
(b) Write short notes on Transport factor.
(c) Large signal current gain.
[5+5+6]
(a) Define a Transistor.
(b) What are the differences between Bipolar Junction transistor & Field effect
Transistor?
(c) Write any two applications of transistor.
[5+7+4]
Explain the construction & working of NPN transistor in detail.
[16]
UNIT – 6: FET Characteristics
1.
(a) How the UJT differs from ordinary PN diode.
(b) Explain the construction of UJT.
(c) Draw and explain the equivalent circuit of UJT.
[4+6+6]
2.
Explain the operation of SCR during forward & Reverse bias.
[16]
3.
With a neat sketch explain the drain source characteristics & transfer characteristics
of depletion type MOSFET.
[16]
4.
(a) Why we call FET as a voltage controlled device?
(b) Write about the broad classification of FET.
(c) Draw the circuit symbol of P Channel N Channel FET.
[4+6+6]
5.
With a neat sketch explain the drain source characteristics and transfer characteristics of
depletion type MOSFET.
[16]
6.
(a) Define DC drain resistance.
(b) Define AC drain resistance.
(c) Define trans conductance.
(d) Define amplification factor.
[4+4+4+4]
UNIT – 7: Transistor Biasing and Thermal Stability
1.
(a) Explain the criteria for fixing operating point.
(b) List out the different types of biasing methods.
2.
3.
4.
[12+4]
Briefly explain fixed bias with Emitter Feed back. Also find the stability of this
bias.
[16]
In a germanium transistor CE amplifier biased by feedback resistor method, VCC
= 20 V, VBE = 0.2 V, β = 100 and the operating point is chosen such that VCE =
10.4 V and IC = 9.9mA, determine the value of RB and RC.
[16]
A transistor with β = 50; VBE=0.7V, VCC=22.5V, and RC = 5.6KΩ is used in biasing
circuit shown in figure 7.1. It is designed to establish the quiescent point at VCE = 12V, IC
= 1.5mA and stability factor S < 3. Find the value of resistor RE1,R1 and R2.
[16]
Figure 7.1
5.
If the various parameters of a CE amplifier which uses the self bias method are VCC
= 12 V, R1 = 10 kΩ, R2 = 5kΩ, RC =1 kΩ, Re =2 KΩ and β = 100, find
(a) The coordinates of the operating point, and
(b) The stability factor, assuming the transistor to be of silicon.
[16]
6.
(a) Explain the simpler way of drawing dc load line.
(b) Calculate the de bias voltage and currents in the circuit shown in figure 7.2
(Neglect VBE of Transistor).
[8+8]
Figure 7.2
7.
(a) What is the use of biasing?
(b) Draw the dc equivalent model.
(c) The circuit as shown in the figure 7.3 has fixed bias using NPN transistor.
Determine the value of base current, collector current, and collector to emitter voltage.
[4+4+8]
Figure 7.3
8.
(a) What is the importance of dc load line?
(b) The figure 7.4 shows that D.C bias circuit of a common Emitter transistor amplifier.
Find the percentage change in collector current, if the transistor with HFE = 50 is replaced
by another transistor with HFE = 150. It is given that the base emitter drop
VBE = 0.6V.
[8+8]
Figure 7.4
9.
(a) Find the collector current and collector to emitter voltage for the given circuit
as shown in figure 7.5.
(b) Can the value of stability factor be less than unity? Explain briefly.
[10+6]
10.
In a CE germanium transistor point for the circuit of potential divider bias arrangement with R2 = RC = 5kΩ, RE = 1 kΩ and R1 = 40kΩ.
[16]
11.
A germanium transistor having β = 100 and VBE = 0.2 V is used in a fixed bias amplifier
circuit where VCC = 16V, RC= 5 KΩ , and RB = 790 kΩ. Determine its operating point.
[16]
UNIT – 8: Small Signal Low Frequency Transistor Models
1.
A transistor used in a CC Circuit as shown in the Figure 8.1. has the following set of h
parameters.
hic = 2 KΩ, hfc = -51, hrc = 1, hoc = 25 × 10−6
Find the values of input and output resistances, current and voltage gains of the
amplifier stage. Use the approximate analysis.
[16]
Figure 8.1
2.
(a) Draw the low frequency hybrid equivalent circuit for CE & CB amplifier.
(b) Give the approximate h-parameter conversion formulae for CB and CC configuration in terms of CE.
(c) Give the advantages of h-parameter analysis.
(d) Give the procedure to form the approximate h - model from exact h - model
of amplifier.
[4+6+3+3]
3.
(a) Write a short notes on miller’s theorem.
(b) Analyze a single stage transistor amplifier using h - parameters.
[8+8]
(a) Compare AV ,Ai, Ri & R0 of CE, CB and CC configuration.
(b) The h-parameters of a transistor used in a CE circuit are hie = 1.0 KΩ , hre
= 10×10−4, hfe = 50, hoe = 100 KΩ. The load resistance for the transistor is
1 KΩ in the collector circuit. Determine Ri,Ro,AV ,Ai in the amplifier stage
(Assume Rs = 1000Ω ).
[4+12]
4.
5.
Derive the expressions for voltage gain, current gain, I/P impedance, O/P impedance of
CC amplifier, using exact & approximate model.
[16]
6.
Derive the expressions for voltage gain, current gain, I/P impedance, O/P impedance of
CE amplifier, using exact & approximate model.
[16]
7.
8.
A transistor used in a CB amplifier has the following values of h - parameters. hib=28Ω ,
hfb = - 0.98, hrb = 510−4 and hob = 0.34×10−6S. Calculate the values of Ri,Ro, Ai and AV , if
the load resistance is 1.2 KΩ. Assume source resistance as zero.
[16]
(a) Explain the effects of source resistance on voltage and current gains of single
stage amplifier.
(b) Design an emitter follower circuits having Ri = 500KΩ, R0 = 20Ω, hfe = 50,
hie = 1 KΩ, hoe = 25 μA/V, find the values of Ai & AV for the circuits.
[8+8]
9.
(a) Draw the low frequency hybrid equivalent circuit for CE & CB amplifier.
(b) Give the approximate h-parameter conversion formulae for CB and CC configuration
in terms of CE.
(c) Give the advantages of h-parameter analysis.
(d) Give the procedure to form the approximate h - model from exact h – model of
amplifier.
[4+6+3+3]
10.
(a) Find the values of hfb and hfc, if the value of hfe of a transistor is 50.
(b) A transistor is connected in CC configuration and its h-parameters are hie =1100 , hre
= 2.5 × 10−4, hfe = 50, hoe = 24mA/V, the circuits uses RL =10 K Ω , and Rs = 1 K Ω ,
calculate gain Ai, input resistance Ri and voltage gain Av of this amplifier.
[4+12]