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Math Help - This seemed easy...at first

  1. #1
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    This seemed easy...at first

    Can someone please help me with a problem?

    I'm studying op-amps and can't quite figure this one out. It's analyzing a noninverting op-amp circuit to find the gain. You shouldn't need any electronic knowledge to figure this out - it's just algebra.

    Here goes:

    Vin = VoutR1/(R1 + R2)
    gain = Vout/Vin = 1 + R2/R1

    I cannot figure out, no matter what I try, how to get from the first equation to the second. Can someone please give me a step-by-step solution?

    Attached is a copy of the entire text for context.

    Thanks!
    This seemed easy...at first-text.png
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  2. #2
    MHF Contributor
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    Re: This seemed easy...at first

    \frac{V_{\text{out}}}{V_{\text{in}}} =\frac{V_{\text{out}}}{V_{\text{out}}R_1/(R_1+R_2)} =\frac{1}{R_1/(R_1+R_2)} =\frac{R_1+R_2}{R_1} =\frac{R_1}{R_1}+\frac{R_2}{R_1}=1+\frac{R_2}{R_1}
    Thanks from joew
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