İzmir University of Economics
ETE 232 Microelectronic Devices and Circuits
LO-2
To do the analysis of simple diode circuits
A. Finding the State of the Diode(s)
D1
Q1. Determine the states of the diodes and the voltage
VX in the circuit given, with
RA = 10 kΩ
RB = 15 kΩ
VA = 20 V
VB = 10 V
VC = 5 V
D2
VX
+
RA
VA
RB
VO
VB
VC
-
(Verify your results).
Q2. Obtain and plot the I-V characteristics of the circuit given below. Assume the diode is ideal.
I
+
V
Circuit parameters:
R1 = 2 kΩ
R2 = 2 kΩ
IA = 1 mA
D
R1
IA
R2
Q3. Assume the diodes are ideal. Plot VO versus VI for
-12 ≤ VI ≤ 12 V, where
R1 = 10 kΩ
R2 = 15 kΩ
R3 = 30 kΩ
V1 = 10 V
V2 = - 5 V
V1
R1
D2
D1
+
+
VI
-
D3
D4
R3
VO
-
R2
V2
B. Diode Circuits
Q4. Consider the circuit given. Assume
R1
vS (t) = Acos 2πf t volts.
where A = 10 V and f = 50Hz, R1 = 1 kΩ, R2=1.2 kΩ,
C = 100 µF.
Without C, determine and plot the output voltage
vO(t).
ii. With C, determine and plot the output voltage vO(t).
iii. Determine the magnitude of the ripple voltage over
the output.
D
+
vS
R2
C
vO
i.
-
1-1
Q5. Design a circuit to generate a steady state voltage vO(t) from the input voltage vS(t) as given
below.
Circuit
to be
designed
VS
+
1V
vS,volts
t
VO
-1 V
2
vO,volts
t
0
Q6. Assuming the diodes in the circuits of Fig. 4.2. are ideal. Determine the labeled current I and
voltage V values. (Hint. Utilize Thevenin’s theorem to simplify the circuits)
Q7. Consider the circuits given below. In each circuit, the input voltage vI is a 1 kHz, 10 V peak
sine wave, i.e., vS (t) = 10cos 2π1000 t volts . Sketch the waveforms observed at vO. (Assume
the diodes are ideal).
vI
(a)
(b)
1-2
(c)
C. Diode Circuits Containing AC Small Signals
Q8. Consider the circuit given on the right. The current I
is a DC current and the input voltage vI is a sinusiodal
signal. The capacitors C1 and C2 are very large.
VDD
I
(a) Determine the DC component of the output
voltage vO.
(b) Use the AC small signal equivalent circuit to show
the small signal component of the output voltage
is
v
v
C1
Rs
C2
+
vS
vO
(c) Assume Rs = 1 kΩ, determine the value of I so that
vo becomes half of vs.
(d) Determine the limit of vs for small signal
assumptions.
-
VDD
Q9. Consider the circuit given in Fig. 3.2. The current I
varies between 0 and 1 mA.
(a) For which value of I, the small signal resistance
values of the diodes are equal.
1 mA
C2
(b) Determine the total output voltage vO for this
current value I found in (a).
vO
(c) For which value of I, the ratio vo/vs is 1/3.
(d) Determine the limit on vs for proper small signal
modeling.
D1
D2
C1
vS
I
1-3
Q10. Consider the circuit given below. Assume the current IQ = 2 mA.
(a) Determine the total output voltage
vO = VO + vo
(b) Determine the limit on vi for small signal
assumptions.
D. Zener Diodes and Voltage Regulators
Q11. Consider the zener diode voltage regulator
given on the right.
Assume the circuit parameters are:
VBB = 10 V, vS (t) = 0.5cos 2π50 t volts ,
R = 100 Ω, RL = 500 Ω,
Zener diode: VZ = 5 V, rz = 50 Ω.
(a) Determine the DC and AC small signal
components of the output voltage vO.
(b) Compare the two terms:
(!"
%&
# )
'
()*+,
and
(!"
%&
# )
'
R
+
iZ
iR
vs
vIN
+
VZ
-
iL
RL
+
vO
Zener
VBB
-
-
+,*+,
(c) Repeat this problem for the case that load
resistance RL is reduced to RL = 500 Ω.
Q12. Consider the zener diode voltage regulator
given on the right.
Assume the circuit parameters are:
VBB = 10 V, vS (t) = 0.5cos 2π50 t volts ,
R = 100 Ω, RL = 500 Ω,
Zener diode: VZ = 5 V, rz = 50 Ω.
Determine the range of RL so that the zener diode
is always operated in the zener region.
R
+
iZ
iR
vs
vIN
+
VZ
-
iL
RL
+
vO
Zener
VBB
-
-
1-4