Physics 375, Laboratory 13
Analog Math
Overview
The purpose of these experiments is to use opamps to perform mathematical operations on input
voltages. Operations include sum, difference, logarithm, differential and integral.
Background
An operational amplifier (opamp) is a differential amplifier with very high gain, very high input
impdance, and very low output impedance. The 741 opamp is an integrated circuit thaat comes
in an 8pin dual inline package (DIP). The connections for the chip looking down with the notch
facing up is:
For large gain, low input current amplifiers used with feedback to the negative input there are two
rules to follow:
1. I
+
=I

=0
.
The input currents are 0.
2. v
+
v

.
The input voltage difference is 0.
For feedback to the negative input, the general steps for analysis are to find the voltage at the non
inverting input and use rule two to assign that same voltage to the inverting input. The next step
is to find the current flowing at the inverting input from any voltage source. Based on rule one all
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 Spring '08
 Johnson,C
 Quantum Physics

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