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ELE 291 – Electrical Fundamentals Laboratory I
Pre-Lab 8 – July 17, 2015
Replacing an Inductor with an Op-Amp Circuit
Name: _____________________________ Date: _______________________
Introduction: Inductors are a useful component when building filters. Unfortunately,
real inductors suffer from several disadvantages. These include size and cost. Audio
systems need inductors much larger than the 10 mH inductors that we used in the
previous lab. A 1 H inductor will cost several dollars and weigh on the order of one
pound, precluding its use in audio systems.
Fortunately, we can build a simple circuit that performs the same as an inductor using an
op-amp, two resistors and one capacitor. In this lab we will build this circuit and verify
that it behaves like an inductor.
Part 1: Build the following circuit on Multisim. This circuit emulates a 100 ohm resistor
in series with a 1 H inductor. For the input use a low frequency square wave (1 Hz). Use
transient analysis to observe the response of the circuit.
XSC1
G
T
A
B
C
D
XFG1
R1
100 Ω
U1
C1
100nF
OPAMP_3T_VIRTUAL
Op Amp Circuit that emulates
an inductor.
R2
100kΩ
Use the formula τ = L/R to determine the theoretical decay time. Does the circuit give
the expected response?
Theoretical τ = ______________
Measured τ = ________________
Part 2: The equivalent circuit is given below. Build this circuit and compare the
response of this circuit to the op amp circuit. That is measure τ.
R3
100 Ω
Equivalent Circuit
L1
1H
R3 = R1
L1 = R1*C1*R2
Measured τ = ________________________