EE 461 Practice Problems for Final Exam
Problem 1 Silicon is doped with phosphorus atoms of 7.5×1016 cm-3. There is no other doping.
(a) Is this n-type or p-type doping? (b) What are the electron and hole concentrations? (c) What
are the electron mobility and hole mobility? (d) What is its resistivity? (The temperature is
300K)
Problem 2 A pn junction diode is fabricated with NA>>ND. What value of doping is required on
the lightly doped side to achieve a reverse breakdown voltage of 750V if silicon breaks down at
a field of 300kV/cm?
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Problem 3 Below is the physical structure of an npn bipolar junction transistor (BJT). The base
is lightly doped p-type. (a) Ignore the hole diffusion from the base to the emitter and describe the
principle of amplification of the BJT transistor with the help of drawing carrier transport from
the emitter to the base and the collector. (b) Draw its circuit symbol with labels of terminals,
voltages, and currents.
n+
p
n
C
E
B
- +
- +
VBE>0
VBC<0
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Problem 4 Draw physical structures and 4-terminal circuit symbols of n-channel enhancementmode MOSFET and p-channel enhancement-mode MOSFET, and their corresponding I-V
characteristic curves schematically. Write the models (equations) of n-channel enhancementmode MOSFET and p-channel enhancement-mode MOSFET. (Assume VTRn=1V and VTRp=1V).
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Problem 5 Draw the circuit diagram of the digital CMOS inverter and describe the principle of
its logic operation qualitatively when input is “Low” (0) and input is “High” (1). Draw its
transfer characteristics and describe its major advantage.
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Problem 6 A common-emitter (C-E) amplifier is shown below with RI=1 kΩ, R1=16 kΩ, R2=30
kΩ, RC=2.2 kΩ, RE=1.3 kΩ, R3=100 kΩ, and VCC=12V. (a) Find its Q-Point (IC, VCE). (b) Find
its small-signal gain. The BJT parameters: βF=200, βO=200, VBE=0.7, and Early voltage VA→ ∞.
VCC
R2
RI
C1
RC
C
∞
C2
∞
+
R3
vi
R1
RE
C3
-
vo
∞
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