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    What is this op-amp configuration?

    Just wondering if someone could describe the function of the circuit below?



    Is it some form of Inductance gyrator?

    The input is the non inverting input.
    It has negative feedback and also low pass filtered positive feedback?

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    Re: What is this op-amp configuration?

    The function of the circuit depends on the internal resistance Rin of the signal source that is applied at the non-inv. input.
    For a pure voltage source (Rin=0) the positive feedback path is useless.


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    •   Alt28th March 2012, 08:17

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    Re: What is this op-amp configuration?

    Please show us your exact schematic. I am kinda not getting.
    It may be gyrator or the form of first order sallen-key topology.


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    Re: What is this op-amp configuration?

    Quote Originally Posted by varunkant2k View Post
    ..................
    .......... or the form of first order sallen-key topology.
    What is this? Sallen-Key stages are always of 2nd order.


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    Re: What is this op-amp configuration?

    ..................
    .......... or the form of first order sallen-key topology.
    What is this? Sallen-Key stages are always of 2nd order
    Sorry I was assuming the form of butter worth -topology.


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    •   Alt28th March 2012, 09:07

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    Re: What is this op-amp configuration?

    Quote Originally Posted by varunkant2k View Post
    Please show us your exact schematic. I am kinda not getting.
    It may be gyrator or the form of first order sallen-key topology.
    Apologies! I had my inputs reversed.

    Here is the correct schematic:



    It seems to be a low pass filter but still what would be the purpose of the 2 resistors connected between the output, ground and non inverting input?



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    Re: What is this op-amp configuration?

    Quote Originally Posted by varunkant2k View Post
    Sorry I was assuming the form of butter worth -topology.
    I know - probably it will be not to important for ECE101, nevertheless it should be clear:
    "Butterworth" is not a term describing any filter topology but rather a certain kind of transfer function response (of at least second order).
    A lowpass of first order has one possible response only - there are no alternatives (except the gain).
    But I agree, ECE101 should show the complete schematic including signal source circuitry and grounding (no open nodes).


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    Re: What is this op-amp configuration?

    Thank you for your replies LvW,

    This is the only schematic I was given.

    Exactly as above, It was actually for a pop-quiz where it was asked to describe its function.



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    Re: What is this op-amp configuration?

    <It seems to be a low pass filter but still what would be the purpose of the 2 resistors connected between the output, ground and non inverting input?>
    One reason, hysteresis..


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    •   Alt28th March 2012, 10:24

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    Re: What is this op-amp configuration?

    Quote Originally Posted by ECE101 View Post
    Thank you for your replies LvW,
    This is the only schematic I was given.
    Exactly as above, It was actually for a pop-quiz where it was asked to describe its function.
    Hi ECE, to answer your question it is necessary to know about the parts values - in particular if positive dc feedback dominates or not.
    (This point was also addressed by varunkant: hysteresis yes/no ?).


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    Re: What is this op-amp configuration?

    well its simply an "INTEGRATOR" , which can be commonly referred to as LPF !
    Dare to think faster than ELECTRON !


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