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>> In this video, I'd like to talk about using the op-amp as a voltage-controlled switch.

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Basically, we put two different voltages Vp and

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Vn into the positive and negative terminals of the op-amp.

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Remember that there's going to be no current going into either

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of these terminals if we assume that this op-amp is ideal.

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So, in this case, what happens is V0 comes out as three different possibilities.

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We've got a plus Vcc and a minus Vcc,

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and then what's going to happen is V0 will equal to zero if V,

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let me put an if statement right here.

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If Vp is equal to Vn,

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it's going to be equal to plus Vcc, if Vp is greater than

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Vn and it's going to be minus Vcc, if the Vp is less than Vn.

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So, in effect, the two voltages that we put in Vp and Vn are going to control

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what our output voltage is and it's basically going to

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rail out between the positive and negative Vcc.

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Now, how could we use this as a switch?

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Remember that no current is coming in from our input circuit right here.

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So, this side is completely isolated from our output side.

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Here's the input and here's the output and these two sides are isolated.

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The current actually comes from our source right here, and it is used for V0.

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So, we would be able to switch something on and off drawing the

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current from the power supply for the op-amp.

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If we wanted to do another possibility such as V0 is equal to zero, if they are equal,

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and let's suppose we want it to be some positive voltage if Vp is equal to Vn,

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and then maybe we would like it to be off if Vp is less than Vn.

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On that case, what you would do is you would hook up your op-amp like

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this with the plus and minus terminals and you'd hook it up to Vcc,

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and then your negative Vcc would just be ground.

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This value, right there.

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That's how you'd be able to make the switch function just a little bit differently.