Measuring Amplitude
Response
Julian Weathersby
Course: AME341
Lab Date: Tuesday, October 16, 2007
Lab Partner: Jeremiah Givens
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Measuring Amplitude Response
Introduction
An opamp, also known as an operational amplifier, is a highgain electronic voltage
amplifier.
The purposes of an opamp are to match measurement resolution, improve the
ratio of the signal to the noise, and to provide impedance matching.
This lab is designed
to test and experiment an opamp and to analyze how an opamp works.
The measured
value for an opamp is the opamp gain, G, which is the low frequency H and is given
by the equation
G
=
H
=
R
f
R
i
(1)
where R
i
is the input resistor and R
f
is the final resistor.
The opamp gain is also
G
=
H
=
e
o
e
i
(2)
where e
o
is the output voltage and e
i
is the input voltage.
The output voltage is measured
at a given frequency and input voltage.
The frequency response is dependent on the input
signal in both open loop and feedback configurations.
An important measurement is the
corner frequency,
ϖ
o, which is
ϖ
o
= 2
pf
o
=
R
i
R
f
A
m
(3)
where A is the gain and
μ
is the time constant.
The corner frequency is found from the
bandwidth,
ϖ
*, which is the equation
*
=
A
m
(4)
Along with the bandwidth is the GainBandwidth Product or GBP, which is the following
GBP
=
Gw
o
GBP
=
R
f
R
i
R
i
R
f
A
m
GBP
=
A
m
(5)
All five equations are used to properly analyze an opamp.
What were to be found was
the corner frequency, the opamp gain, the bandwidth, and the GainBandwidth Product
of a LM741 opamp.
Procedure
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 Fall '07
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