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| Circuit Built |
The first lab required the implementation of a summing amplifier. For this type of amplifier the output voltage V(out) = - R3/R1 * (Va+Vb). So if R3 and R1 are the same value the input voltages would just add but would be the inverse of the summation of the voltages. We built this summing amplifier by using an operational amplifier.
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| Results |
Above is a result of supplying different voltages into the circuit. R3 and R1 are the same values so V(out) should be the inverse of the summation of Va and Vb. For the most part the summing amplifier worked until it reached 3V+ where it began to saturate.
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| Graph of Results |
Above is the graph of the input voltage vs the output voltage. As can be seen, at 3V+ it begins to saturate which would not be ideal in this case.
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| Circuit built |
The next circuit built was a difference amplifier. Using an operational amplifier once again, and four identical resistors (10K Ω) allowed us to theoretically state that Vout = -(Va - Vb).
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| Results |
Because we used identical resistors that voltages going in to the op amp would come out to be the difference. In this scenario we used 1V for Vb and when different voltages was supplied for Va the voltage out of the amp would just be -(Va-1). The voltage out would also be the inverse of the difference because we are used an inverting op amp.
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| Graph of results |
As can be seen by the graph, Vout saturates at 4.23V and -3.49V.
Conclusion:
Today, we learned about some new operational amplifier circuits. Theses circuits include an inverting amplifier, summing amplifier, non-inverting amplifier, and a difference amplifier.
Inverting Amplifier:
An inverting amplifier reverses the polarity of the input signal while amplifying it.
Vout = -(Rf/R1)*Vi
Summing Amplifier:
A summing amplifier simply adds the voltages going into the op-amp but also reverses the polarity.
Vout = -((Rf/R1) *V1 + (Rf/R2) *V2 + (Rf/R3) *V3)
Non-inverting Amplifier:
A non-inverting amplifier provides a positive voltage gain.
Vout = (1+Rf/R1) * V1
Difference Amplifier:
A difference amplifier amplifies the difference between two inputs but rejects any signals common to the two inputs.
Vout = R2/R1 * (V2-V1) if R1/R2 = R3/R4.
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