GTU Computer Engineering (Semester 3)
Basic Electronics
December 2014
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary


Explain in brief the following:
1 (a) 1 Diffusion Length.
1 M
1 (a) 2 Conversion Efficiency.
1 M
1 (a) 3 Voltage Stability Factor.
1 M
1 (a) 4 Peak Inverse Voltage.
1 M
1 (a) 5 Critical wavelength.
1 M
1 (a) 6 Pinch off Voltage.
1 M
1 (a) 7 Base Spreading Resistance.
1 M
1 (b) Explain in detail the energy band diagram of insulator, semiconductor and Conductor.
7 M

2 (a) State and explain Pauli's Exclusion Principal.
7 M
2 (b) Derive continuity equation and explain its importance.
7 M
2 (c) If a donor impurity is added to the extent of one atom per 108 germanium atoms, calculate its resistivity at 300°k. If its resistivity without addition of impurity is 44.64 Ω-cm,comparing two values, comment on result. Ge atom per cm3 is 4.4?10 22 and μn = 3800 cm2 /V-sec.
7 M

3 (a) Draw switching waveform of diode and explain following terms.
a) Storage time
b) Transition time
c) Reverse recovery time.
7 M
3 (b) A Ge diode has a contact potential of 0.2V, while concentration of acceptor impurity atoms is 3×1020 per m3 , calculate for a reverse bias of 0.1V the width of depletion barrier. Assuming cross sectional area of the junction as 1mm2 , calculate the transition capacitance value. Assume\[\bigcup_{1}^{0}\] = 16 for Ge.
7 M
3 (c) (i) Explain peace wise linear diode model.
(ii) FET as Voltage Variable Resistor.
7 M
3 (d) What is the purpose of filter? Explain capacitor filter with waveforms.
7 M

4 (a) Draw CE transistor configuration and give its input and output characteristics. Also derive the relation between current gain of CE,CB and CC configurations.
7 M
4 (b) Explain thermal runaway and derive the condition for thermal stability.
7 M
4 (c) For circuit of Figure No - 1, calculate the minimum and maximum value of emitter current when ? of transistor varies from 75 to 150. Also calculate the corresponding values of collector to emitter voltage. Take VBE = 0.3V, Rb =10kq, Rc = 50q , Re = 100q, Vcc = +6V.

7 M
4 (d) Explain compensation techniques related with transistor biasing.
7 M

5 (a) State and prove Miller's theorem and its dual.
7 M
5 (b) Describe briefly the construction and working of p channel Enhancement MOSFET. Draw its characteristic and transfer curve.
7 M
5 (c) Draw class B push-pull system and derive maximum conversion efficiency
7 M
5 (d) (i) Compare Load Regulation and Line Regulation.
(ii) Figure -2 shows a basic CE amplifier. If Rs =100q and RL =4kq , determine AVS , AIS ,Ri , and Ro Use hie =1100Y, hre =2.5×10-4 ,hfe =50 and hoe =1/40kY.

7 M



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