Gujarat Technological University 2010-3rd Sem Certification Computer Engieering Computer Engineering Basic Electronics - Question Paper
GUJARAT TECHNOLOGICAL UNIVERSITY
B.E. Sem-III Regular / Remedial Examination December 2010
Seat No. Enrolment No.
Subject Name: Basic Electronics Date: 13 /12 /2010 Time: 10.30 am - 01.00 pm
Total Marks: 70
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) Answer the following: 07
(i) What is semiconductor? Define a hole in semiconductor
(ii) State the Pauli exclusion principle
(iii) Sketch the piecewise linear characteristics of p-n diode (iv ) Define an electron volt (eV)
(v) State the mass-action law as an equation and in word.
(vi) What is cutin voltage? Write approx. value of cutin voltage for silicon and germanium diode
(vii) Write the equation for the volt-ampere characteristic a photo diode
(b) Draw and explain bridge rectifier circuit with capacitorfilter. Draw necessary 07 waveforms.
Q.2 (a) Draw the circuit of CE configuration of transistor. ExplainInput and output characteristics. Derive a = P / P+1 (b) (i) Draw symbol and explain briefly the working principle Breakdown diode and Tunnel diode
07
04
03
04
03
03
02
02
(ii)Write principle and applications of light emitting diode
OR
(b) (i) Describe the Hall effect. Which properties of a Semiconductor are determined from Hall effect experiment?
(ii) Explain electrical properties of germanium and silicon ( conductivity ,the mobility and the energy gape)
Q.3 (a) Draw following diode circuits with input and output Waveforms:
(i) Voltage doublers circuit
(ii) Positive clipping circuit
(iii) Negative clamper circuit
(b) (i) A 5kQ load is fed from a bridge rectifier connected with a transformer
04
03
secondary whose primary is connected to 460V, 50 Hz supply. The ratio of number of primary to secondary turns is 2 : 1. Calculate dc load current ,dc load voltage , ripple voltage and PIV rating of diode,
(ii) A 100F capacitor when used as a filter has 12 V dc Across it with a terminal load resistor of 2.5kQ. If the rectifier is full wave and supply frequency is 50 Hz calculate the percentage of ripple in the output
OR
(a) Explain the h-parameter model of CE amplifier with derive the expression for Ai , Av , Ri , Ro
Bypass resistor RE and 07
Q.3
(b) Find hre in terms of the CB h-parameters
Q.4 (a) What is biasing? Why biasing is required for transistor? List biasing methods for transistor. Draw and explain the circuit of voltage divider biasing (b) Where CC configuration is used? Draw circuit of CC and CB configuration of transistor. Compare current gain ,voltage gain ,input impedance and output impedance of both
OR
07
Q.4 (a) A CE amplifier using npn transistor has load resistance RL connected between 07 collector and Vcc supply of + 16 V For biasing resistor , Ri is connected between Vcc and base Resistor R2 = 30 kQ is connected between base and ground. RE =
1kQ. Draw the circuit diagram and calculate the value of R1 , Rc ,stability factor
S if Vbe = 0.2V, Ieq = 2 mA , Vceq = 6 V , a = 0.985 (b) Design a fixed bias circuit using silicon npn transistor Which has pdc = 150. The 07 dc biasing point is VCE = 5V And Ic = 5 mA Supply voltage is 10V.Write advantages and disadvantages of fixed bias circuit.
Q.5 (a) (i) Define the pinch-off voltage Vp .Sketch the depletion region before and after 03 pinch-off.
(ii) Sketch the cross section of a P-channel enhancement MOSFET .Show two 04 circuit symbol for MOSFET (b) Draw circuit of an idealized class-B push-pull power amplifier and explain its 07 operation with the help of necessary waveforms.
OR
Q.5 (a) (i) Compare different types of power amplifier based on conduction angle , 04 position of Q-point , efficiency and distortion
(b) A MOSFET has a drain- circuit resistance Rd of 100K and operates at 20 kHz. 07 The MOSFET parameters are gm = 1.6 mA/V, rd = 44K , Cgs = 3 Pf Cds = 1 pF ,Cgd = 2.8 pF.Calculate the voltage gain of this device .
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2
Seat No. :__Enrolment No._
GUJARAT TECHNOLOGICAL UNIVERSITY
B.E. Sem-III Remedial Examination March 2010
Subject Name: Basic Electronics Date: 09 / 03 / 2010 Time: 3.00 pm - 05.30 pm
Total Marks: 70
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (A) What is transition capacitance of a p- n junction diode ? For a step graded 07 junction prove that the expression for the transition capacitance of a diode is same as the capacitance of a parallel plate capacitor.
(B) How does the designer minimize the percentage variation in IC , due to variation 07 in ICO and VBE and due to variation in P in transistor amplifier circuit.
Q.2 (A) A 230 V , 50 Hz AC voltage is applied to the primary of a 5:1 step down 07 transformer which is used in a bridge rectifier having a load resistor of a value 470 Q. Assuming the diodes to be ideal , determine the following
(a) DC output voltage
(b) DC power deliver to the load
(c) Maximum value of output current
(d) Average value of output current
(e) RMS value of output current
(f) Output frequency
(g) PIV of diode
(B) Define 07
(a) Drift velocity of electron
(b) Electric field
(c) Photovoltaic potential
(d) Photo excitation
(e) Photo ionization
(f ) Intensity of electric field (g) Reverse recovery time of diode
OR
(B) Define 07
(a) Electron volt
(b) Potential
(c) Critical wavelength for semiconductor
(d) Mean life time of carrier
(e) Mobility of electron
(f) Volt equivalent of temperature
(g) Pinch off voltage of FET
Q.3 (A) A bar of silicon 0.2 cm long has a cross sectional area of 9 x 10-8 m2 , heavily 04 doped with phosphorus. What will be the majority carrier density resulting from doping if the bar is to have resistance of 2 kQ ? Given for silicon at room temperature :
|in= 0.14 m2/V-sec, |ip= 0.05 m2/V-sec, ni= 1.5 x 1010 /cm3, q =1.602 xl0-19 C (B) Give minimum four comparisons of following semiconductor devices
06
(1) Tunnel diode with conventional diode.
(2) LED with conventional diode.
(3) LED with photo diode.
(C) Prove that current density is proportional to product of charge density , mobility 04 of charge and electric field intensity.
OR
Q.3 (A) A static resistance of 4 Q is observed in an ideal germanium diode at room 04 temperature. The current flowing through the diode is 50mA. If the forward biased voltage is 0.2V , volt equivalent temperature is 26mV , calculate :
(i) Reverse saturation current
(ii) Dynamic resistance of diode
(B) Draw output waveform of following circuits. Consider input of 20V (peak to 06 peak), 10kHz sine wave and assume ideal diode.
(i)
V1
j 111-
+
+
5 V
ikn
Vi
Vo
(ii)
+
+
1|jF
Vi
Vo
-5 V
I
(C) Explain the hall effect in semiconductor. How hall effect is considered in 04 measurement of mobility and conductivity?
Q.4 (A) Derive relationship between Odc and pdc of a transistor.
04
(B) Explain any one circuit which is used to improve the input impedance of the 06 amplifier.
|
(C) Determine whether or not the transistor in below circuit is in saturation. Assume 04 P =50 and Vce( sat) =0.3V, Vbe =0.7V. |
 |
|
OR |
Q.4 (A) Compare various transistor amplifier configurations.
04
06
(B) Draw and explain the input and output characteristics of p-n-p silicon transistor in CB configuration. Indicate cut off , saturation and active regions.
(C) Two stage amplifier circuit is mentioned below. Calculate overall voltage gain 04 Av. Take hie = 2.2K ,hfe = 60 , hre= 2.5 x 10-4 ,hoe= 2.5 A/V, Rc= 3.3 kQ ,
Re= 4.7kQ, Rs= 1 kQ, Vcc=+12V.
 |
+ |
(A) For following circuit , calculate the minimum and maximum value of emitter 06 current when P of transistor varies from 75 to 150 . Also calculate the corresponding values of collector to emitter voltage. Take VBE = 0.3V, Rb= 10kQ , Rc= 50 Q , Re= 100 Q, Vcc= +6V.
Q.5
+6V
>5on
Rc
>iokn
Rb
qi
Re
>ioon
(B) Explain with neat circuit diagram, the working of a transformer coupled class A 04 power amplifier.
(C) Compare FET with BJT in terms of advantages, disadvantages, construction and 04 operation.
Q.5 (A) Describe briefly the construction and working of p channel enhancement 06 MOSFET. Draw its characteristic and transfer curve.
(B) A class B push pull amplifier supplies power to a resistive load of 15Q. The 06 output transformer has a turns ratio of 5:1 and efficiency of 78 %.
Assume hfe =25 and Vcc =18V.
Obtain :
(a) Maximum power output
(b) Maximum power dissipation in each transistor
(c) Maximum base current for each transistor.
(C) Explain the signification of following parameters in evaluating the regulation 02 performance of a DC series regulator
(a) Input regulation factor ( Stability factor ) SV
(b) Temperature stability factor ( Temperature co efficient ) ST
*************
4
Seat No. :__Enrolment No._
GUJARAT TECHNOLOGICAL UNIVERSITY
B.E. Sem-III Remedial Examination March 2010
Subject Name: Basic Electronics Date: 09 / 03 / 2010 Time: 3.00 pm - 05.30 pm
Total Marks: 70
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (A) What is transition capacitance of a p- n junction diode ? For a step graded 07 junction prove that the expression for the transition capacitance of a diode is same as the capacitance of a parallel plate capacitor.
(B) How does the designer minimize the percentage variation in IC , due to variation 07 in ICO and VBE and due to variation in P in transistor amplifier circuit.
Q.2 (A) A 230 V , 50 Hz AC voltage is applied to the primary of a 5:1 step down 07 transformer which is used in a bridge rectifier having a load resistor of a value 470 Q. Assuming the diodes to be ideal , determine the following
(a) DC output voltage
(b) DC power deliver to the load
(c) Maximum value of output current
(d) Average value of output current
(e) RMS value of output current
(f) Output frequency
(g) PIV of diode
(B) Define 07
(a) Drift velocity of electron
(b) Electric field
(c) Photovoltaic potential
(d) Photo excitation
(e) Photo ionization
(f ) Intensity of electric field (g) Reverse recovery time of diode
OR
(B) Define 07
(a) Electron volt
(b) Potential
(c) Critical wavelength for semiconductor
(d) Mean life time of carrier
(e) Mobility of electron
(f) Volt equivalent of temperature
(g) Pinch off voltage of FET
Q.3 (A) A bar of silicon 0.2 cm long has a cross sectional area of 9 x 10-8 m2 , heavily 04 doped with phosphorus. What will be the majority carrier density resulting from doping if the bar is to have resistance of 2 kQ ? Given for silicon at room temperature :
|in= 0.14 m2/V-sec, |ip= 0.05 m2/V-sec, ni= 1.5 x 1010 /cm3, q =1.602 xl0-19 C (B) Give minimum four comparisons of following semiconductor devices
06
(1) Tunnel diode with conventional diode.
(2) LED with conventional diode.
(3) LED with photo diode.
(C) Prove that current density is proportional to product of charge density , mobility 04 of charge and electric field intensity.
OR
Q.3 (A) A static resistance of 4 Q is observed in an ideal germanium diode at room 04 temperature. The current flowing through the diode is 50mA. If the forward biased voltage is 0.2V , volt equivalent temperature is 26mV , calculate :
(i) Reverse saturation current
(ii) Dynamic resistance of diode
(B) Draw output waveform of following circuits. Consider input of 20V (peak to 06 peak), 10kHz sine wave and assume ideal diode.
(i)
V1
j 111-
+
+
5 V
ikn
Vi
Vo
(ii)
+
+
1|jF
Vi
Vo
-5 V
I
(C) Explain the hall effect in semiconductor. How hall effect is considered in 04 measurement of mobility and conductivity?
Q.4 (A) Derive relationship between Odc and pdc of a transistor.
04
(B) Explain any one circuit which is used to improve the input impedance of the 06 amplifier.
|
(C) Determine whether or not the transistor in below circuit is in saturation. Assume 04 P =50 and Vce( sat) =0.3V, Vbe =0.7V. |
|
|
OR |
Q.4 (A) Compare various transistor amplifier configurations.
04
06
(B) Draw and explain the input and output characteristics of p-n-p silicon transistor in CB configuration. Indicate cut off , saturation and active regions.
(C) Two stage amplifier circuit is mentioned below. Calculate overall voltage gain 04 Av. Take hie = 2.2K ,hfe = 60 , hre= 2.5 x 10-4 ,hoe= 2.5 A/V, Rc= 3.3 kQ ,
Re= 4.7kQ, Rs= 1 kQ, Vcc=+12V.
|
+ |
(A) For following circuit , calculate the minimum and maximum value of emitter 06 current when P of transistor varies from 75 to 150 . Also calculate the corresponding values of collector to emitter voltage. Take VBE = 0.3V, Rb= 10kQ , Rc= 50 Q , Re= 100 Q, Vcc= +6V.
Q.5
+6V
>5on
Rc
>iokn
Rb
qi
Re
>ioon
(B) Explain with neat circuit diagram, the working of a transformer coupled class A 04 power amplifier.
(C) Compare FET with BJT in terms of advantages, disadvantages, construction and 04 operation.
Q.5 (A) Describe briefly the construction and working of p channel enhancement 06 MOSFET. Draw its characteristic and transfer curve.
(B) A class B push pull amplifier supplies power to a resistive load of 15Q. The 06 output transformer has a turns ratio of 5:1 and efficiency of 78 %.
Assume hfe =25 and Vcc =18V.
Obtain :
(a) Maximum power output
(b) Maximum power dissipation in each transistor
(c) Maximum base current for each transistor.
(C) Explain the signification of following parameters in evaluating the regulation 02 performance of a DC series regulator
(a) Input regulation factor ( Stability factor ) SV
(b) Temperature stability factor ( Temperature co efficient ) ST
*************
4
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Attachment: |
| Earning: Approval pending. |
