Operational Amplifier howtos

The operational amplifier is one of the most useful analog ICs available, and one of the most daunting for beginners and experienced engineers.

Above is a diagram of an op-amp in a closed loop non inverting configuration. Probably the most used configuration. Lets assume this is an ideal amplifier. R1 is the input and R2 is the feedback. When R1 = R2 the circuit is in unity(meaning input = output).

To calculate output use the following formula.


R3 can be calculated by the following.


learn more about operational amplifiers in the docs

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  1. That is an inverting configuration, and with the + input at ground, you are going to need a split supply (both positive and negative voltages) and for a positive voltage in you get a negative voltage out. I don’t think that is the most common opamp configuration these days, people like single-supply circuits.

  2. The semiconductor companies have produced all the free documentation
    you’ll ever need about op-amps, including free books. Just google and read:

    “Op Amps for Everyone”, TI
    “Handbook of Operational Amplifier Applications”, TI SBOA092a
    “Op Amp Applications Handbook”, ADI

    The ADI book is available as a dead tree, but it’s also on their site.

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