Model Question Paper 2014,

ECE 101, Electron Devices & Circuits

Max Marks: 100 Duration: 180 min.Answer all questions to the point. Missing data may be suitably assumed with justification.

1. i) Expand and define PIV. [2ii) Sketch a Full Wave Rectifier. [2iii) A FWR circuit with a 1 k load operates from a 230 V, 50 Hz supply thru a 10-to-1 centre-tapped transformer. The Si diodes have VD = 0.7 V. What is the peak voltage of the rectified output? What fraction of a cycle each diode conducts? What are the average output voltage and the average current in the load? [6

2. The parameters of the transistor in the circuit are β = 150, VA = ∞. i) Design a bias stable circuit with its Q-point in the centre of the load line. ii) Find its small signal voltage gain Gv. [8

3. Two identical diodes with are connected back to back and a 15 V the applied across them. The current Io flows thru the diodes. i) Show that e(V

1/nV

T) + e(V

2/nV

T) = 2, where V1 and V2 are voltage drops across the

diodes. ii) If, Io = 0.1 A and VT = 25 mV, the emission coefficient n = 2, calculate the current in the circuit and the voltage across each diode.[8

4. Photodiode vs LED - Compare in terms of their principles and applications? [6

5. What is Early Effect? What phenomenon causes it? Sketch the CE output characteristics and indicate Early voltage. [8

6. Compare and contrast the three configurations of a BJT amplifier in terms of current and voltage gains and input and output impedances.[6

7. Sketch a CB amplifier circuit and its ac equivalent circuit. Develop

expressions for Av, Gv, Rin and Rout.[108. In the circuit shown voltage at the emitter was -0.7 V. If b = 50, find IE,

IB, and IC and VC. [10

9. A CC amplifier is used to connect a source with Rsig = 10 k to a load RL

= 1.0 k. The transistor is biased at I = 5 mA and utilizes resistance RB

= 40 k and has b = 100 and VA = 100 V. Find Rin, Ro, Av, Ai. [1010. List the breakdown mechanisms in a MOSFET and explain how it is

protected against static voltage. [411. The FET amplifier in figure has Vt = 2.0 V, kn’(W/L) = 1 mA/V2, VGS = 4

V, VDD = 10 V and RD = 3.6 kΩ. Find ID and VD. Evaluate gm at the bias point and the voltage gain. [10

12. Depict a common Source Amplifier. Develop its small signal equivalent circuit. Derive expressions for Av, Gv, Rin and Rout. [10

13. Design the circuit shown to obtain an ID of 80 A, given Vt = 0.6 V, nCox

= 200 A/V2, L = 0.8 m and W = 4 m. Assume = 0. Sketch its small signal equivalent circuit. [10

14. The CS amplifier shown has Vt = 1.0 V, kn’(W/L) = 2 mA/V2. Find VGS and ID and VD. and gm, ro for VA = 100 V. Draw its small signal equivalent circuit. [10