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Tutorial - 2: Questions on PN junction with Solutions (EDC)

Electronic Devices and Circuits

Unit – 1 : Tutorial – 2 (22nd July 2015)
Topic:  PN junction under open circuit condition 
Submission Date : 31st July 2015 (before 12:30 pm)

Short Questions:
1. What is the significance of arrow direction on symbol of PN junction?
2. Draw the V – I characteristics of Ideal diode and find the resistance in forward bias and reverse bias from the characteristics
3. Define Diffusion phenomenon. Discuss whether diffusion occurs due to majority or minority carriers in PN junction.
4. Define Drift phenomenon. Discuss whether drift occurs due to majority or minority carriers in PN junction.
5. Draw the diagram of PN junction at open circuit condition under equilibrium and indicate depletion region widths, open circuit voltage and electric field direction and neutral regions.

Long Questions:
6. Prove that the depletion region penetrates more into lightly doped side of PN junction than heavily doped.
7. For a PN junction, calculate the change in contact potential if the doping on P-side is increased by a factor of 1000 and doping on N-side is unaffected.
8. For a Germanium diode with ND = 1016 donors/cm3 and NA = 3 x 1018 /cm3. Calculate for a PN junction under open circuit
(a) Built in potential (Vo)
(b) Width of potential barrier
(c) Maximum electric field
9. Define forward and reverse bias. Mention unique characteristics of PN junction under forward and reverse bias.
10. For a Step graded PN junction with NA > ND, Draw a neat sketch for volume charge distribution (ρv), electric field intensity (ε) and effective voltage for holes.