Tufts University
School of Engineering
Department of Electrical and Computer Engineering
ES3  Introduction to Electrical Circuits
Fall 2009
Experiment #4
Amplification, Impedance, and Frequency Response
Purpose:
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View Full DocumentThe purpose of this lab was to use the breadboard and circuit material to determine the thevenin
equivalent circuit for an amplifier chip, as well as to use oscilloscope to measure the amount by
which the amplifier increases the gain. Finally, a bode plot was created to show the relation of
gain to frequency (where the frequency scale was logarithmic).
Introduction:
In this lab, knowledge of certain equations was necessary in order to calculate the voltage gain:
=
Av voutvin
And the gain:
=
Av 20log10voutvin
In order to find the impedance of a capacitor, one must know that:
=
ZC 1jωC
Or that the impedance of a capacitor equals the inverse of the square root of 1 multiplied by the
angular velocity and the capacitance.
In order to create the correct sinusoidal waveform for voltage on the oscilloscope, the
equation:
=
Vt vasin2πft
should be known. In this lab specifically, the value for
va
will be 0.025 V (0pk), and the value
for
f
should be 1000 Hz.
The equation to calculate the theoretical voltage across the 50Ω resistor in the circuit:
In order to find the thevenin resistance of the amplifier circuit, the equation from lab 3,
=
*
+
Vout Vth RLRL Rth
should be known, where R
L
is the resistance across the speaker.
Materials
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 Fall '08
 A
 Decibel

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