7/27/2019 A5 - 1st Test Paper (1)

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CMR Institute of TechnologyFeb-Jul 2013 Basic Electronics (10ELN25) Sem 2 - A & B Prof. H. N. Shankar

Assignment # 05 1st Test paperSubmission Due: Mar. 12, 2013

Note:

Sketch diagrams wherever relevant. Explain your notations explicitly and clearly. Write neatlyand legibly. Shabbily written assignments will not be accepted.

An incomplete assignment is not acceptable for submission. Once you submit your assignment, you will be expected to answer all the questions there

INDEPENDENTLY. You may be asked to answer any question of the assignment in the class.

Your evaluated first test answer scripts will be given to you after the submission if thisassignment.

Answer all questions

1. (i) The n-type semiconductor is formed by doping with _____ impurities.

(A) trivalent; (B) pentavalent; (C) tetravalent; (D) intrinsic semiconductor.

(ii) The voltage beyond which IF increases rapidly is _____ voltage.

(A) saturation; (B) breakdown; (C) cut-in; (D) blocking.

(iii) The reverse saturation current is mainly due to _____.

(A) minority carriers; (B) majority carriers; (C) both majority and minority carriers; (D) only holes.

(iv) The depletion region has charges. T/F

(v) There can be a net movement of charges across even an unbiased pn-junction. T/F

(vi) The penetration of the depletion region is less on the ______ side.

(A) p; (B) lightly doped; (C) n; (D) heavily doped.

(vii) The magnitude of the junction potential increases when reverse biased. T/F

(viii) In its usual operating mode, the Zener diode has a high resistance. T/F(ix) For the same forward current, the drop across a diode increases with temperature. T/F

(x) Diffusion capacitance is seen when the pn-junction is reverse biased. T/F

2 a. Explain the diffusion mechanism in an unbiased pn-junction and the resultant formation of thedepletion region with relevant sketches.

b. The forward current of a pn-junction diode is 15 mA at 35C. Find its forward dynamic resistance at295K.

3 a. How does the temperature of the junction affect the forward- and reverse-biased pn-junction? Givethe relevant relationships.

b. With relevant sketches, explain the dc load line and its use in dc analysis for apn-junction diode.

4 a. Explain avalanche and Zener breakdown mechanisms with relevant sketches.

b. A Si pn-junction has a reverse saturation current I0 = 34 nA at 295K. At what temperature will I0be 50nA?

5 a. A Si pn-junction diode has I0 = 32 nA at 298K. Find the diode current when the drop across it is (i)0.4 V in forward bias at 325 K; and (ii) 6 V in reverse-bias at 20 C.

b. Define reverse breakdown voltage, power derating factor, reverse recovery time and fall time.

6 a. A 5 V supply is across a series combination of a Si diode, a Ge diode and 110 resistor. Find the

powers dissipated in each diode and the load resistor at room temperature.b. What are the factors on which the barrier potential depends?