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Old Sep 4th 2017, 05:48 AM   #1
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Op Amp circuit and RC circuit transient analysis.

I have unable to figure out this 2 problem.

Please help me understand them.

For the first one #1, (Op Amp), I know that all ideal opAmp has V+ = V- but the problem states that Vout = A ( V+ - V-). If there were equal, Vout will be 0 then.

For the second one #2 ( I am really have a hard with how to redraw the circuit and derive the differential equation.

I have been out of school for some time so I am a bit rusty.

Please help
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Op Amp circuit and RC circuit transient analysis.-screenshot_20170903-181133-01.png  
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Old Sep 6th 2017, 01:02 PM   #2
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The first looks like a controlled gain circuit (So A shouldn't figure in final analysis). I think you should be able to solve that with Kirchoff's laws. https://en.wikipedia.org/wiki/Kirchh...s_circuit_laws. The voltage $\displaystyle V^{+} = V_{in}$ as there is no voltage drop across RS as no current is flowing through the inputs of the op amp. R1 and R2 comprise a voltage divider which you can work out the voltage drop between them from ohms law. That should give you V- and from there you should be able to calculate $\displaystyle V_{out}$ and the gain $\displaystyle \frac{V_{out}}{V_{in}}$.

The second just looks like a capacitor resistance network. From google the current formula for a capacitor is $\displaystyle I = C \frac{dV}{dt}$. I would assume the two $\displaystyle V_{dd}$ points are connected, as they are at the same potential, even though they are not drawn that way. You should be able to solve this using Kirchoff's current laws.
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Last edited by kiwiheretic; Sep 6th 2017 at 11:14 PM.
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amp, analysis, circuit, transient



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