ME 530.241: Electronics and Instrumentation
Lab 4: Impedence, RC Circuits, and All That
Louis L. Whitcomb and Kyle B. Reed
*
Department of Mechanical Engineering
The Johns Hopkins University
Spring 2009
Apparatuses
Multimeter, Tektronix PS280 DC Power Supply, Tektronix TDS3014B oscillo
scope, Tektronix CFG 253 function generator, leads, breadboard
1
PreLab Exercises
SHOW ALL YOUR WORK. No credit will be given unless your work is completely (and neatly)
presented.
1. Exercise 4.51 of [1].
2. Exercise 4.59 of [1].
3. Exercise 4.54 of [1].
4. Exercise 4.57 of [1].
5. Consider the
ﬁrst order lowpass ﬁlter
circuit shown in Figure 1.
(a) Draw the the circuit shown in Figure 1 (just the circuit, omit the probe leads).
(b) Use phasor notation and impedance methods to analyze the circuit to determine the
magnitude
and
phase
of the output voltage
V
C
(
t
) for an input voltage from the signal
generator
V
S
(
t
) = 1
.
0 cos(
ωt
).
i. Give an expression for the magnitude of the output as a function of frequency.
ii. Give an expression for the phase of the output as a function of frequency.
(c) Use your results from the previous question to:
i. Compute the 3dB frequency in units of Hz  i.e. the frequency at which
V
C
(
t
) =
1
√
2
V
S
(
t
). This will be
f
3
dB
for Question 4 in Section 2 of the lab.
ii. Compute the magnitude of the output at the 3dB frequency.
iii. Compute the phase of the output at the 3dB frequency.
(d) Plot (using Matlab, Excel, or your favorite plotting method) the following data.
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 Spring '09
 Okamura
 Mechanical Engineering, RC Circuits, Highpass filter, Lowpass filter, Tektronix, experimentally observed magnitude, Louis L. Whitcomb

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