EDC-Test Yourself
UNIT-I & II
SET-1
1. a. Derive the expression for acceleration, Velocity and displacement of a charged particle placed
in an electric field E.
b. Two parallel plates of a capacitor are separated by 4 cms. An electron is at rest initially
at the bottom plate. Voltage is applied between the plates, which increases linearly from
0v to 8v in 0.1 m.sec . If the top plate is +ve, determine
i. The speed of electron in 40 n.sec.
ii. The distance traversed by the electron in 40 n.sec.
2. a. Explain the process of break down of a p -n junction diode due to
i. Avalanche effect
ii. Zever effect
b. Find the concentration of holes and electrons in a p -type silicon at 3000 K assuming resistivity
as 0.02 cm. Assume p 475m / v sec , ni 1.45 10
2 10 3
per cm .
3. a. Give the block diagram of CRO and explain about each block in detail.
b. In a electro static deflecting CRT the length of the deflection plates is 2 cm , and spacing
between deflecting is 0.5 cm , the distance from the centre of the deflecting plate to the screen
is 20 cm. The deflecting voltage is 25 V . Find the deflection sensitivity, the angle of deflection
and velocity of the beam. Assume final anode potential is 1000 V.
4. a. What are general specifications of P-N junction diode?
b. The voltage across a silicon diode at room temperature (300 0 K) is 0.7. volts when 2mA current
flows through it. If the voltage increases to 0.75V calculate the diode current (assume
V T =26mA).
5. a. An electron is moving perpendicular to magnetic field ‘B’. Derive the expression for adius
‘R’ of the trajectory and period of rotation T.
b. The electrons emitted from the thermionic cathode of a cathode ray gun are accelerated by a
potential of 400V. The essential dimensions are L=19.4cm, l=1.27cm and d=0.475 cm.
Determine deflection sensitivity. What must be the magnitude of a transverse magnetic field
acting over the whole length of the tube in order to produce the same deflection as that
produced by a deflection potential of 30V?
6. a. Explain the formation of depletion region in an open -circuited pn-junction with neat ketches.
b. A pn-junction diode has a reverse saturation current of 30 A at a temperature
0
of 125 C . At the same temperature find the dynamic resistance for 0.2V bias in forward and
reverse direction.
SET-2
1. a. Derive the expression for transit time (tow) and final velocity V in the case of an electron traversing in
uniform electric field E.
b. What is Hall Effect? Derive an expression for Hall coefficient?
An electron with a velocity of 3 x 105 ms-1 enters an electric field of 910 v/m making an angle of 60 with
0
2. a.
the positive direction. The direction of the electric field is in the positive Y direction. Calculate the time
required to reach the maximum height.
b. Calculate the conductivity of copper having density 8.9 gm / cm3 and mobility 34.8 cm 2 / v sec .
Atomic weight of copper is 63.57 while it has 1 valance electron per atom. Assume the value of
M 1.66 1027 kg .
3. a. List out the advantages and disadvantages of both electrostatic and electromagnetic deflection system?
b. Explain the term transition capacitance CT of p-n junction diode.
4. a. Explain the terms
i. Potential ii. Electron Volt
iii. Charge Density iv. Current Density
b. Derive the expression for transition capacitance CT of a diode.
5. a. Derive the expression for the electrostatic deflection sensitivity in the case of CRT.
b. Explain why p-n junction contact potential cannot be measured by placing a voltmeter across the diode
terminal.
6. a. Compare electrostatic and electromagnetic deflection sensitivity in all respects.
b. With reference to the P-N junction diode.
i. Distinguish between drift current and diffusion current.
ii. Distinguish between diffusion capacitance and transition capacitance.
7. a. With the help of a necessary equations show the trajectory of an electron is cycloid when it is placed in
perpendicular electric and magnetic fields.
b. Compare the characteristics of p-n junction diode, Zener diode and tunnel diode.
8. a. Determine the velocity and kinetic energy of an electron accelerated through potential of 3 Kv.
b. How do you determine whether a given semiconductor is p-type or n-type? Explain the principle with
necessary equations.
UNIT-III
1. a. What are the important characteristics of a rectifer circuit? Explain them briefly.
b. A diode whose internal resistance 20 is to supply power to a 100 load from 110 V (rms) source of
supply. Calculate:
i. Peak load current ii. d.c load current iii. a.c load current
iv. The percentage regulation from no load to the given load. [Aug’ 07]
2. a. Derive the expression for ripple factor for FWR with L-Section filter. Explain the necessity of a bleeder
resistor.
b. A 3K resistive load is to be supplied with a d.c. voltage of 300V from a.c. voltage of adequate magnitude
and 50Hz frequency full wave rectification. The LC filter is used along the rectifier. Design the bleeder
resistance, turns ratio of transformer, VA rating of transformer PIV rating of diodes. [Aug’ 07]
3. a. Draw and explain the circuit diagram of FWR with L-section filter. What is its ripple factor?
b. A HWR circuit has filter capacitor of 1200 µF and is connected to a load of 400 . The rectifier is
connected to a 50 Hz, 120 Vrms Source. It takes 2 m sec for the capacitor to recharge during each cycle.
Calculate the minimum value of the repetitive surge current for which the diode should be rated. [Aug’ 07]
4. a. Define the terms as referred to FWR circuit
i. PIV
ii. Average d.c. voltage
iii. RMS current
iv. Ripple factor
b. A full wave rectifier (FWR) supplies a load requiring 300 V at 200 mA. Calculate the transformer secondary
voltage for
i. A capacitor input filter using a capacitor of 10 F
ii. A choke input filter using a choke of 10 H and a capacitance of 10 F . Neglect the resistance of
choke. [May’ 06, Aug’ 06, May’ 07]
81.2
5. a. Show that for a full wave rectifier %
R
1 f
RL
b. Draw the circuit diagram of a bridge rectifier circuit with -section followed by L-section filter and explain
its operation. [Nov’ 04, Jun’ 05, Nov’ 05, Aug’ 06]
6. a. Derive the expression for ripple factor in a full wave rectifier using an inductor filter.
b. Compare the performance of series inductor, L-Section and -Section filters.
c. In a full wave rectifier using an LC – filter L=10 H , C=100 F and R L = 500 . Calculate Idc ,Vdc ,
for an input vi 30sin 100 t . [Nov’ 04, May’ 06]
7. a. Why filter circuit is necessary with rectifiers. Give the list of different filters used in rectifier and their merits
and demerits. [Nov’ 05]
b. Discuss a full wave rectifier with -filter.
UNIT-IV
1. a. Summarize the sailent features of the characteristics of BJT operating in CE, CB and CC configurations,
b. Calculate the values of I E , dc and dc for a transistor with IC =13µA, I B =200mA, ICBO =6µA . Also
determine the new level of IC which will result from reducing IB to 100mA. [Aug’ 07]
2. a. Sketch the circuit symbols for
i. n-channel JFET ii. p-channel JFET
iii. n-channel enhancement type MOSFET iv. p-channel enhancement type MOSFET
v. n-channel depletion type MOSFET and vi. p-chanel depletion type MOSFET.
And compare JFET and MOSFETs.
b. Why FET in called unipolar device and is called as voltage operated device. What are the important
characteristics of FET. [Aug’ 07]
3. a. Describe a set up to obtain the output characteristics of a transistor in CE configuration. Indicate the
various regions of operation on the output characteristics.
b. Explain the principle of MOSFET in depletion mode. With neat sketches and output characteristics.[May’ 07]
4. a. Draw the two transistor version of an SCR and explain its firing characteristics with this circuit.
b. Explain the working principle of UJT with its characteristics. [May’ 06, Jun’06, May’ 07]
5. a. A transistor operating in CB configuration has I c 2.98 mA , I E 3.00mA and I CO 0.01 mA what
current will flow in the collector circuit of this transistor when connected in CE configuration with a base
current of 30 A .
b. The reverse saturation current in a transistor is 8 A . If the transistor common base current gain is 0.979,
calculate the collector and emitter current for 40 A base current. [May’ 06]
6. a. Explain the input and output characteristics of the transistor in CE configuration.
b. Given an NPN transistor for which 0.98, I CO 2 A and I EO 1.6 A . A common emitter
connection is used and VCC 12v and RL 4.0k . What is the minimum base current required in order
that transistor enter in to saturation region. [Nov’ 05]
7. a. Define , , of a transistor show have they are related to each other.
b. Define I CBO and I CEO . How are they different? How are they related? Are the typically close in
magnitude? [May’ 06]
8. a. What are the different configurations of BJT. Explain?
b. What is the order of magnitude of I CBO for Si transistor and Ge transistor. How does I CBO vary with
temperature? [Nov’ 05]
9. a. What is meant by base width modulation. Explain how input characteristics can be effected due to this
effect.
b. The current gain of a transistor in CE circuit is 49. Calculate CB current gain and find the base current
where the emitter current is 3 mA. [Nov’ 05]
10. a. Why transistor is considered as current control device. Explain
b. In a transistor if emitter junction is forward biased and collector is reverse bias explain its operation.
c. Explain why 1 for a given transistor. [Jun’ 05]
11. a. Draw the drain characteristics of depletion type MOSFET. Explain clearly different operating regions in
characteristics with proper reasoning.
b. Describe the construction of a light-emitting diode and explain its operational mechanism. [Aug’ 07]
12. a. Draw the input and output characteristics of transistor in CE configuration with regions of operations and
explain. Show how h-parameters can be determined graphically.
b. Derive the relation between and [Jun’ 05, Aug’ 06]
13. a. Explain the mechanism of current flow in a PNP and NPN transistor.
b. In a transistor operating in active region, although the collector junction is reverse biased, the collector
current is quite large explain. [May’ 06, Aug’ 06]
14. a. Explain active region, saturation region and cut-off region in transistor characteristics.
b. Differentiate between NPN and PNP transistors.
c. Explain the input and output characteristics of the transistor in CC configuration with diagrams. What is the
inference from these characteristics? [Aug’ 06]
UNIT-V
1. a. Explain bias compensation using sensistors.
b. In the circuit shown, if I C 2mA and VCE 3V . Calculate R1 and R3 . [May’07, Aug’ 06 & 07]
2. a. Compare BJT, JFET and MOSFET in all respects.
b. For the JFET circuit with voltage divider bias as shown below, calculate VG , VS , VD and VDS . If
VGS = -2V . [Aug’ 06 & 07]
3. a. Explain how do you set a Q point in a self biased JFET.
b. For the FET self biased circuit shown in figure 5, calculate the values of RD and RS to obtain the bias
condition. The maximum drain current is 10mA and VGS =-2.2V at I D =5mA . [Aug’ 07]
4. a. Explain in detail about thermal runaway and thermal resistance.
b. For the circuit shown figure, determine I E , VC and VCE . Assume VBE 0.7V . [May’07]
5. a. Draw a BJT fixed bias circuit and derive the expression for the stability factor ‘S’.
b. An NPN transistor with 50 is used in a common emitter circuit with VCC = 10V,R C =2K . The bias
is obtained by connecting a 100K resistance from collector to base. Assume VBE = 0.7V . Find
i. The quiescent point and
ii. The stability factor, S. [Aug’ 07, May’ 06]
6. a. Draw a voltage divider bias JFET circuit and explain how the Q point is set in it.
b. For the circuit shown in figure, determine the value of I C and VCE. Assume VBE=0.7V and =100. [Aug’ 06]
7. a. Distinguish between TRIAC, SCR and DIAC.
b. Draw the static characteristics of SCR for different gate currents and briefly explain? [Apr’ 06]
8. a. Explain the reasons for keeping the operating point of a transistor as fixed.
b. For the circuit shown, calculate VE , I E , I C and VC . Assume VEE 0.7V . [Aug’ 06]
9. a. Draw the circuit diagram of a saw tooth wave form generator using UJT and explain its operation.
b. What is meant by Pinch off voltage pinch of locus of JFET? Mark Pinch of locus form drain characteristic.
[Aug’ 06, Nov’ 05]
10. a. Draw a BJT self bias circuit and obtain the expression for the stability factor ‘S’.
b. A Germanium transistor is used in a self biasing circuit configuration as shown below with Vcc=16V,
Rc=1.5k and 50 . The operating point desired is VCE 8V and I C 4mA . If a stability factor
S=10 is desired, calculate values of R 1 , R 2 and R E of the circuit. [May’ 06]
11. a. Give the UJT symbol and simplified equivalent circuit with external resistors included.
b. Draw UJT emitter characteristics and mention various region.
c. If VE < Vp and VE Vp for these condition how UJT works.
d. If 0.8VBB =15V and VD 0.7V . Find the value of Vp . [Jun’ 05]
12. a. Briefly discuss about the following opto electric devices.
i. Photo diode
ii. Photo transistor
b. List out different types of MOSFETS and compare their salient features. [Jun’ 05]
UNIT-VI
1. a. What are the advantages of h-parameters?
b. A CE amplifier has following circuit 2 and transistor parameters. R C =10K, R E =2K,
h ie =2K, h fe =60, hoe 10 mhos, hre 110 4
. Assuming RE is adequately bypassed by a capacitor
C E . Calculate AI , AV . [Aug’ 06]
2. a. Draw the equivalent current of a CE amplifier in terms of h-parameters and obtain the expressions for
voltage gain and current gain.
b. Consider a single stage CE amplifier with RS 1K , R1 50 K , R2 2 K , RC 1K , RL 1.2 K ,
h fe 50 and hie 1.1K as shown in figure. Find AI , AV , RI , RO . [Aug’ 06]
3. a. Draw the circuit for darlington pair and derive the expressions for A I , A V , R I and R 0
b. The figure shows a CE amplifier with collector to base bias. Calculate AI , AV , R I . The transistor
6 4
parameters are h ie =1.1K, h fe =50, h oe 25 10 A / V, h re =2.5 10 . [Aug’ 06 & 07]
4. a. Draw a low frequency equivalent circuit for a CC amplifier and derive the relations for the current gain,
voltage gain and input resistance in terms of h-parameters.
b. In the common collector circuit in figure, the transistor parameters are hie 1.2 K and h fe 101 .
Calculate input and output resistances, voltage gain and current gain. [May’ 06]
5. a. Draw the circuit diagram of CE amplifier with emitter resistance and obtain its equivalent hybrid model and
derive expressions for AI , RI , AV . Use approximate analysis.
b. Determine Au , AI , Ri , RO for CE amplifier using n-p-n transistor with hie 1200, hre 0, h fe 36 ,
6
hoe 2 10 mho, RL 2.5k , RS 500 . (neglect the effect of biasing circuit) [Aug’ 06]
6. a. Compare transistor amplifier configurations related to A I , A V , input resistance R I and out resistance R O .
b. For a CE amplifier if R 2 = R S 1000 and h ie = 1100, h re 2.5 104 , h fe 50, h oe 25µa / v
find A I , R i , A V , A VS , A1S . [Nov’ 05]
7. a. Draw the circuit diagram of a emitter follower circuit and derive expression of A V and A I using hybrid
model.
b. For a two stage cascade amplifier circuit shown below figure. Calculate A1 and A V . Assume h ic 1100r,
h rc 1,h fe 51, h oc 25µa / V . [Apr’ 06]
UNIT-VII
1. a. Explain negative feedback with the help of the emitter follower as an example. Why is the emitter follower
so called?
b. The gain of an amplifier is decreased to 10,000 with negative feedback from its gain of 60,000. Calculate
the feedback factor. Express the amount of negative feedback in dB. [Aug’ 07 & 06]
2. a. Explain the concept of feedback with block diagram.
b. An Amplifier with negative feedback gives an output of 12.5V with an input of 1.5V. When feedback is
removed, it requires 0.25V input for the same output. Find
i. Value of voltage gain without feedback
ii. Value of , if the input and output are in phase and is real. [Aug’ 07, 06]
A
3. a. State three fundamental assumptions which are made in order that the expression Af
1 A
be satisfied exactly.
b. An amplifier has a value of R in 4.2K, AV =220 and 0.01 . Determine the value of input resistance
of the feedback amplifier.
c. The amplifier in part (a) had cut-off frequencies f1 =1.5 KHz and f 2 501.5 KHz before the feedback
path was added. What are the new cut-off frequencies for the circuit? [Apr’ 07, Aug’ 06]
4. a. Define Desensitivity.
b. For large values of D, what is Af ? What is the significance of this result?
c. An amplifier has a mid-frequency gain of 100 and a bandwidth of 200 KHz .
i. What will be the new bandwidth and gain if 5% negative feedback is introduced?
ii. What should be the amount of negative feedback if the bandwidth is to be restricted to 1MHz ?
[Apr’ 07, May’ 06]
5. a. Briefly discuss about the effect of feedback on amplifier Bandwidth.
b. Draw the frequency response of amplifier with and without feedback and show the bandwidth for each case
and how these two curves are related to gain bandwidth product.
c. We have an amplifier of 60db gain. It has output impendence Zo=10k. It is required to modify its output
impendence to 500 by applying negative feedback. Calculate the value of the feedback factor also find the
percentage change in the over all gain, for 10% change in the gain of the internal amplifiers.
[Apr’ 06, May’ 05, Jun’ 05, Nov’ 05]
6. a. Classify the amplifiers based as feedback topology and give their block diagram. How the input and output
impendence are effected in each case.
b. Draw the circuit diagram of a current feed back circuit and derive expressions for voltage gain and output
resistance, and input resistance. [Aug’ 06, Apr’ 06]
7. a. Discuss briefly about various characteristics of an amplifier which are modified by negative feedback.
b. An RC coupled amplifier has a voltage gain of 1000. f1 50 Hz, f 2 200 KHz and a distortion of 5%
1 1
without feedback. Find the amplifier voltage gain, f ,f
1 2 and distortion when a negative feedback is
applied with feedback ratio of 0.01 . [Feb’ 08]
8. a. Explain the concept of feedback as applied to electronic amplifier circuit. What are the advantages and
disadvantages of positive and negative feedback?
b. An amplifier has a voltage gain of 1000. With negative feedback, the voltage gain reduces to 10. Calculate
the fraction of the output that is feedback to the input. [Feb’ 08]
9. a. Draw the circuit diagram of voltage shunt feedback and derive expressions for input and output resistances.
b. An Amplifier has an open loop gain of 800 and a feedback ratio of 0.05. If the open loop gain changes by
20% due to temperature, find the percentage change in closed loop gain. [May’ 06]
10. a. What do you understand by feedback in amplifiers? Explain the terms feedback factor and open loop gain.
b. Calculate the gain, input impedance, output impedance of voltage series feedback amplifier having A=300,
R i =1.5K, R O =50K and 1/12 . [May’ 06]
UNIT-VIII
1. a. Draw the circuit diagram of a RC phases shift oscillator using BJT. Derive the expression for frequency of
oscillators.
b. Classify different type of oscillators based on frequency range.
c. Why RC oscillators are not suitable for high frequency applications.
[Feb’ 08, Apr’ 07, Aug’ 06 & 07, Apr’ 06, Sep’ 06, May’ 06, Jun’ 05, Nov’05]
2. a. Show that the gain of Wien bridge oscillator using BJT amplifier must be at least 3 for the oscillations to
occur.
b. In a transistorized Hartley oscillator the two inductances are 2H and 20H while the frequency is to be
changed from 950 KHz to 2050 KHz. Calculate the range over which the capacitor is to be varied.
[Apr’ 07, Aug’ 06, Apr’ 06, May’ 06, Jun’ 05, Nov’ 04 & 05]
3. a. Discuss and explain the basic circuit of an LC oscillator and derive the condition for the oscillations?
b. A crystal has L 2H , C 0.01PF and R 2k . Its mounting capacitance is 2PF . Calculate its
series and parallel resonating frequency? [Feb’ 08, Aug’ 07, Nov’ 04 & 05]
4. a. What are the factors that affect the frequency stability of an oscillator? How frequency stability can be
improved in oscillators?
b. Derive an expression for frequency of oscillations of Hartley oscillator using BJT. [Aug’ 07, Jun’ 03, Nov’ 04]
5. a. Derive an expression for frequency of oscillation of transistorized Colpitts oscillator.
b. A quartz crystal has the following constants. L 50mH , C1 0.02 PF , R 500 and C2 12 PF .
Find the values of series and parallel resonant frequencies. If the external capacitance across the crystal
changes from 5PF to 6PF, find the change in frequency of oscillations. [May’ 06, Nov’ 04]
6. a. Classify various oscillators based on output waveforms, circuit components, operating frequencies and
feedback used.
b. A phase shift oscillator is to be designed with FET having g m =5000 s, rd =4k while the resistance in
the feedback circuit is 9.5k. Select the proper value of C and RD to have the frequency of oscillations as
5KHz. [Aug’ 06, Jun’ 03]
7. a. Derive the expression for frequency of oscillations in RC-phase shift oscillator using BJT.
b. A crystal has L 0.1H , C 0.01PF , R 10K and CM 1PF . Find the series resonance and Q-
factor. [Feb’ 08]
8. a. What is piezoelectric effect? Explain the working of crystal oscillator.
b. A crystal oscillator has L 0.4H , C 0.085PF and Mounting capacitance CM 1PF with
R 5k . Find series and parallel resonant frequencies. By what percent does the parallel resonant
frequency exceed the series resonant frequency? Also find the Q-factor of the crystal. [Apr’ 07]
9. a. What type of feedback is employed in oscillators? And what are the advantages. Discuss the conditions for
sustained oscillations.
b. Find the capacitor C and h fe for the transistor to provide a resonating frequency of 10KHz of a phase
shift oscillator. Assume R1 25k , R2 60k , Rc 40k , R 7.1k and hie 1.8k . [Aug’ 06]
10. In the phase shift oscillator R1=R2=R3=1M and C1=C2=C3=68 PF. What frequency does the circuit oscillate.[Jun’
04]
11. A phase shift oscillator using a transistor has the parameter values R L=3.3K, R=5.6K and C=0.01F. Calculate
frequency of oscillations required for sustaining the oscillations. [Jun’ 04]
12. Mention advantages and limitations of Wien-Bridge oscillator? The R-C circuit of a Wien-Bridge oscillator consist of
R1 R2 220K and C1 C2 250 pF . Determine the frequency of oscillations? [Jun’ 03]
13. For the Colpitts oscillator C1=750PF, C2=2500PF and L=40H. Determine the operating frequency and feedback
fraction. [Jun’ 03]
14. A tuned collector has a fixed inductance of 100H and has to be tunable over the frequency band of 500KHz to
1500KHz. Find the range of variable capacitor to be used. [Jun’ 03]
15. a. Why the LC oscillator are not suitable for low frequency applications. Explain the principle of working of
basic LC oscillators.
b. Find C and hfe of a transistor to provide f o of 50 KHz of a RC transistorized phase shift oscillator. Given
R1=22k, R2=68k, Rc=20k, R=6.8k and hie=2k. [Jun’ 03]
16. In the Wien Bridge oscillator R1=R2=220K and C1=C2=250 PF. Determine the frequency of oscillations. [Nov’ 02]
17. The AC equivalent circuit of crystal has these values: L=1H, C=0.01PF, R=1000, Cm=20PF. Calculate fs and fp of
the crystal. [Nov’ 02]
18. The resonant circuit of a tuned collector transistor oscillator has a resonant frequency of 5MHz. If the value of
capacitance is increased by 50%, calculate the new resonant frequency. [Nov’ 02]
19. Find the operating frequency of a transistor Hartley oscillator if L1=1001H, L2=1mH, mutual inductance between the
coils M=20H and C=20PF. [Nov’ 02]
20. The tuned collector oscillator circuit used in the local oscillator of a radio receiver makes use of an LC tuned circuit
with L=58.61H and C1=300pF. Calculate the frequency of oscillations. [Nov’ 02]
21. Calculate the operating frequency and feedback fraction for Hartley oscillator. The mutual inductance between the
coils M=20H, L1=1000H, L2=100H, C=20PFI. [Nov’ 02]
22. Determine the operating frequency and feedback fraction for colpitts oscillator C1=0.001F, C2=0.01F, L=15H.
[Nov’ 01]