### EEGR215 Take Home EXAM 4

**EEGR215 Take Home EXAM 4**

EEGR215 Take Home EXAM 4

Show all your work. Exam is to be completed on your own. Any exams that appear to be copies will each be given a 0.

T/F (5 Points each)

1. [T] [F] A reduction in the depletion region width means that the diode has been reversed biased.

2. [T] [F] To forward bias a diode, a positive potential must be supplied to the n-type region of the diode.

Questions (18 Points each)

1. In the diagram below, EF - Ei = −0.4eV in the p-region and EF - Ei = 0.3eV in the n-region of the diode. Assuming the

material is silicon, what is the built in potential Vbi?

2. (a) In the depletion approximation for the pn diode, why do the holes and electrons not continue to diffuse until the all the

electrons and holes carrier concentrations are evenly dispersed throughout the device? (b) In the bulk regions of a pn diode,

what is the value of the electric ield. Explain your answer.

3. A diode is doped withNA = 1016cm3 on the p -type side andND = 1017cm3 on the n -type side. (a) What is the depletion-layer

width? (b) What are the values of xp and xn? (c) What is the value of the built-in potential of the junction? (d) What is the value

of the maximum electric ield, εMax?

4. (a) In the circuit below, ind the voltages across each resistor assuming an ideal diode. (b) Find the voltages across the

resistors assuming a constant voltage drop diode with Vbi = 0.7V.

5. Using the graph below, plot the load line and ind the Q-point for the diode circuit in the igure below if V = 9V and R = 3kΩ.

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