Electrical Engineering Department
Alfred University
ELEC 354 Electronics I
Fall Semester 2007
Midterm Exam
SOLUTION
Total points: 18 points
1.- ( 3 points) For a pn junction with ND = 1016 cm-3 and NA = 10 15 cm -3, assuming room temperature and
ni = 1.5 X 10 10 cm-3 , find:
a) the build-in voltage
b) the width of the depletion region
c) assuming a junction area of 2000 μm2 find the value of Cjo
2.- (2 points) Find the resistivity of
a) an intrinsic silicon
b) a p-type silicon with ND = 1017 cm-3
Note:
Assume room temperature ( ni = 1.5 X 10 10 cm-3 )
For intrinsic silicon: μn = 1350 cm2/V.sec and μp = 480 cm2/V.sec
For doped silicon: μn = 1110 cm2/V.sec and μp = 400 cm2/V.sec
3.- (5 points) Analyze the following circuit to determine all node voltages and branch currents. Assume β = 200
4.- (3 points) Assuming the voltage drop in the diode is 0.7 V, sketch the transfer characteristic vo vs vI
5.- (5 points) In the following circuit sketch the voltage waveforms at the points A, B, C and D. Assume that the
charging time of the capacitor is much larger than the period of the input signal. Indicate the values in the voltage
amplitudes. Assume the voltage drop in the diodes is 0.7 V.