differential amplifier

This video is a super short description of the functional use of the op amp differential amplifier circuit. More info at www.ece.utah.edu/~ece1250

>> Now, let's talk about how a differencing or subtracting amplifier works.

I've drawn the whole amplifier here,

it's a combination of a inverting and

a non-inverting amplifier with the two separate voltages Vs1 and Vs2.

You can see that what happens right here is you have your feedback loop.

Right here, I'm not going to scribble in the feedback loop.

There's the feedback loop going to the negative connection and that's the feedback,

we have one voltage right here connected onto the negative feedback.

So, Vs1 right here is going to be the negative part of our equation.

We can see that because the gain on the negative feedback is minus R2 over R1.

This other term is going to be the positive part or Vs2.

We can see that we only have positives right here.

So, that's the gain that we're going to have on Vs2.

We could basically look at that like bringing in Vs1 and multiplying it

by the first gain, bringing in Vs2 and multiplying it by the second gain,

and then adding them up.

The only cool thing is that gain one is negative and gain two is positive,

so we end up essentially subtracting off,

part of Vs1 from Vs2.

That gives us our output voltage.

As with all of our op-amps.

The V0 is limited between the two power supply voltages,

Vcc and minus Vcc.