YOUR NAME________________________________
Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology
6.012 Electronic Devices and Circuits
Exam No. 1
Notes:
1. Unless otherwise indicated, assume room temperature and that kT/q is 0.025 V.
You
may also approximate [(kT/q) ln 10] as 0.06 V.
2. Open book; 6.012 text and any other notes permitted.
3. All of your answers and any relevant work must appear on these pages. Any
additional paper you hand in will not be graded.
4. Make reasonable approximations and assumptions.
State and justify any such
assumptions and approximations you do make.
5. Be careful to include the correct units with your answers when appropriate.
6. Be certain that you have all eight (8) pages of this exam booklet and make certain
that you write your name at the top of this page in the space provided.
6.012 Staff Use Only
PROBLEM 1
PROBLEM 2
PROBLEM 3
TOTAL
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Problem 1
(24 points)
Consider a uniformly doped ptype silicon bar 1 mm by 1 mm in cross section.
You are told that the equilibrium hole concentration, p
o
, in this sample is 10
16
cm
3
, and
that it contains boron with a concentration of 1.5 x 10
16
cm
3
along with another dopant
of unknown identity and concentration. The minority carrier lifetime is 10
5
s, n
i
= 10
10
cm
3
, µ
e
= 1600 cm
2
/Vs, and µ
h
= 600 cm
2
/Vs.
(a)
What is the type and concentration of the other dopant? Suggest a possible
identity for this other dopant.
Type:
Concentration:
cm
3
Possible identity:
(b)
What is the room temperature resistivity, , in this sample?
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 Fall '03
 Prof.CliftonFonstadJr.
 Pn junction, µm, Vab, depletion region width

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