Download GTU BE/B.Tech 2019 Winter 3rd Sem Old 131101 Basic Electronics Question Paper

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Subject Code: 131101

GUJARAT TECHNOLOGICAL UNIVERSITY

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Instructions:

1. Attempt all questions.

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2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Answer the following questions:

1. (a) Sketch the piecewise linear characteristics of PN junction diode. [07]

   (b) What is cut-in voltage? Write approx. value of cut-in voltage for silicon and germanium diode. [07]

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2. (a) Define Thermal resistance. [07]

   (b) Define Mean life time of a carrier. [07]

3. (a) What do you mean by PIV (Peak Inverse voltage)? Enlist the value of PIV for different rectifiers. [07]

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   (b) What is depletion region in PN junction diode. [07]

4. (a) Explain Zener breakdown phenomena. [07]

   (b) Explain the Hall effect and obtain the expression of Hall coefficient. List the applications of Hall effect. [07]

   OR

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   (b) Draw and explain bridge rectifier circuit with capacitor filter. Draw necessary waveforms. [07]

5. (a) The resistivity of intrinsic silicon is 3x10³ O-cm at 30°C. Calculate the intrinsic concentration at 100°C. Assume µ_n=0.13m²/V-sec and µ_p=0.05m²/V-sec at 30°C. [07]

   OR

   A silicon sample is non-uniformly doped with donor impurity of 10¹⁶m^-3. A current density of 10mA/cm² is generated when electric field of 3V/cm is applied across it. Find the concentration gradient at 27°C. Given: µ_n=1500 cm² /V-sec. [07]

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6. (a) Draw the circuit of Common Emitter configuration of transistor. Explain input and output characteristics. Also derive a = ß / (ß+1). [07]

   (b) For the circuit shown in Figure (1),explain working of the circuit and draw output waveform for given input signal. Also draw transfer characteristics. [07]

   OR

   (b) What is biasing? Why biasing is required for transistor? List biasing methods for transistor. Draw and explain the circuit of voltage divider biasing. [07]

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7. (a) The silicon transistor used in the circuit of Figure (2) has V_CEsat=0.2V, V_BEsat=0.8V, V_BE(active)= 0.7V, V_{BE(cut in)}=0.5V and ß=100. (I) Show that the transistor is in saturation. (II) Calculate the value of R_E for which the transistor just comes out of saturation. [07]

   (b) Define stabilization factors; S, S', and S''. Also derive expressions for S and S' for self bias transistor circuit. [07]

8. (a) The transistor used in the circuit of Figure (3) has the following parameters: h_ie =500 O, h_re = 2.4 x 10^-4, h_fe = 60 and h_oe = 1/40 kO. Calculate : [1]V_o/V_S [2]I_R' [3] R_i Assume all capacitors to be very large. [07]

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   OR

   (b) Draw circuit of an idealized class B push pull power amplifier and explain its operation with the help of necessary waveforms. [07]

9. (a) Calculate the dc bias voltages and currents for the circuit shown in Figure (4). [07]

   (b) Derive expressions for A_i, R_i, A_v and R_o for CE emitter follower circuit. [07]

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   (b) Draw and explain working of diode compensation circuit for V_BE for self-stabilization in amplifier circuit. [07]

   OR

10. (a) Draw structure of n-channel JFET and explain its working. [07]

    (b) Draw a structure of p-channel MOSFET. Explain its working for enhancement type. Also draw and explain drain characteristics and transfer curve for the same device. [07]

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Date: 30/11/2019
Total Marks: 70

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