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Electronics (1) EE 220 First Exam
Q1:
Given a uniformly doped n-type semiconductor having an area of A=10-5 cm2. If a 4 volt voltage is applied across the device and the device
current is 2mA where the length of the device is L=0.1cm. If n=1360 cm2/V.s and p=400 cm2/V.s find (a) the doping of the sample (b)
the resistivity of the material.
Q2:
 E /(2 kT )
Given a uniformly doped semiconductor having donor doping of 1015cm-3 and if ni  4.88 1015  T 3 / 2 e g
.
o
a) Calculate the electron and hole concentrations and the resistivity of the sample if T=450 K, Eg=1.02eV, n=400 cm2/V.s, p =150
cm2/V.s, and k  8.62  10 5 eV/K
b) If an electric field of (104 V/cm) is applied on the sample, calculate the velocity of the electrons and holes.
Q3:
For a PN silicon diode has NA=3x1017 cm-3 and ND=8x1017 cm-3. Assume the following parameters for Silicon: ni=1010 cm-3, 0=8.85x1014
F/cm, R=Ks=11.8, q=1.6x10-19, KT/q=26mV, KT=26meV
Calculate
1) The build-in voltage
2) Depletion region width
3) Maximum electric field (0)
4) np0, nn0 , pp0 and pn0
5) plot n(x), p(x) and (x) showing their numerical values in each region
6) Explain why the diode reverse bias current is much less than the forward bias current?
EE220- Electronics I Electrical Engineering Department
Q4:
Given the following
energy band diagram
for Silicon where
ni=1010 cm-3 and
Eg=1.12eV
0
x1
L/2
x2
L
x
Ec
Ei
Ef
0.15eV
0.8eV
1)
2)
3)
4)
Find n and p at .x=0, x1, L/2, x2 and L
What is the type of the material at x=0, x1, L/2, x2 and L
Plot electric field (x) and potential V(x)
Find the total current at x=L/2
EE220- Electronics I Electrical Engineering Department
Ev
Electronics (1) EE 220 Second Exam
Q1)
The diode in the circuit of Fig.1 has the following I-V-characteristic equation
iD=10-3(vD2 –0.25) Amp for vD>0.5, Then:
a) Find and Draw the DC load line and the Q-point conditions (i.e. IDQ & VDQ)?
b) Find the dynamic resistance of the diode rd?
c) Find VL(t)?
vD
1K
Fig.1
+
1K
1m sin(0t) A
10V
~
Q2:
For the circuit shown, if vi=20sin(600t) V
a) Sketch vi and vR identify all critical
points on the plot
vi
b) Find the output DC voltage (vR)
c) Mention two applications for this
circuit
+
VL(t)
iD(t)
1K
1mA
-
1:1
-
~
+
1k
1:1
EE220- Electronics I Electrical Engineering Department
+
vR
-
200F
Q3)
A) (5 points)
For the circuit shown in Fig. 1, assume that the turn-on voltage of the diodes is 0.7V. Plot and
explain the output voltage (Vout) as a function of time “label all points in the figure”
2V
D1
Vin
+
Vout
20V
Vin
-5V
~
500
time
-
Figure (1)
Vin
B) (3points)
For the circuit shown, assume
VD=0.7V , VR=4V and the input is
as shown. Plot Vo(t)
+
10V
Vin
time
+
~
-
Vo

VR
-10V


Figure (2)
Q4)
For the circuit of Fig.3, if β =200 and VBEQ=0.7V. Find the operating currents IBQ, ICQ, and IEQ, assuming VCEsat=0.24V.
50KΩ
1KΩ
Fig.3
5.7V
EE220- Electronics I Electrical Engineering Department
10V
Electronics (1) EE 220 Final Exam
Time:2hr
Answer All Questions. Show your work in details, and find final numerical answer
Q1:
(a) A PN diode has Na=4x1017 cm-3 and ND=3x1018 cm-3. Calculate the depletion region width and build-in voltage. Assume ni=5x1010 cm3
, 0=8.85x10-14 R=Ks=11.8, q=1.6x10-19, KT/q=26mV (4 marks)
D2
D1
500
(b) For the circuit shown in Fig. 1,
assume that the turn-on voltage of the diodes
is 0.7V. If Vin=10sin(300t) volt, plot and explain
the output voltage (Vout) as a function of time
“label all points in the figure” (9 marks)
Vout
Vin
4V
6V
Fig.1
Q2:
For the MOSFET shown in Fig.2, if kn = 2x10-3A/V2,
VTN = 2V and r0=100KΩ.
Find the following:
1) Find the values of VGSQ, IDSQ, VDSQ, and gm?
2) Find and plot the DC and AC Load Line-equations? 20K
3) Draw the small signal model for the circuit ?
4) Find the voltage gain VL/Vi?
vi
+24V
1.5k
4.8M
C
C
+
vL
7.5k
+
~
-
2.4M
Fig. 2
500

Zin
EE220- Electronics I Electrical Engineering Department
Zout
-

Q3:
For the circuit shown, assume VBEQ=0.7V, =100
hre=0, hoe=1/ro=10-4 S find
1) ICQ and VCBQ ?
2) Draw the small signal model for the circuit?
3) Find small-signal gain (vL / vi)?
-5V
10V
3k
2k
C
100
vi
+
~
-
3k
-
Fig. 3
Q4:
For the circuit shown, assume =120, VBEQ=0.7V
find
a) IBQ, and dynamic resistance (r)
b) Draw AC-equivalent circuit
c) Find Rc which provide maximum symmetrical
swing
d) Find small-signal gain (vL / vi)
+10V
Rc
C
10k
vL
C
+
vi
3k
~
-
4k
200
EE220- Electronics I Electrical Engineering Department
+
vL
CE

Q5)
For the emitter follower circuit of Fig.3, if β=100 and VBEQ=0.7V. Find the following:
a) Determine the maximum symmetrical swing conditions of the Q-point?
b) Find the values of R1 and R2 that will give us the Q-point conditions in (a)?
c) Find and Sketch the DC and AC Load Lines? Identify on the plot all critical points.
10V
R2
400Ω
1KΩ
VS
~
R1
1KΩ
1.5KΩ
+
VL
-
Fig.3
Q6) For the circuit shown in Fig 4, assume =100, VBEQ=0.7V
find
a) ICQ, VCBQ and dynamic resistance (r)
100
b) Draw AC-equivalent circuit
c) Draw DC and AC load lines and
identify on them the Q-point and the cut-off,
+
active and saturation and reverse regions.
vi ~
d) Find small-signal gain (vL / vi)
C
vL
8k
1k
4k
EE220- Electronics I Electrical Engineering Department
10V
3k