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>> Now, let's review what an inverting summer does.

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We can start with the inverting amplifier shown here and then add on

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an additional voltage source, which has its own resistance and its own voltage.

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Then, what's going to happen is Vo is going to be the combination of

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these two voltages, as shown here.

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As with all of our op-amp circuits,

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the Vo is limited between the two power supply voltages as always.

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We can look at this circuit as having two separate gains A and B,

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or minus A and minus B.

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And then, what we do is bring in Vs1 and multiply it by minus A,

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bring in Vs2 and multiply that by minus B,

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and bring the two of these together and add them,

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that's the summer part.

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That gives us V out.

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So, that's how an inverting summer works.