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  1. #1
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    Variable gain amplifier

    Hello,
    We need a variable gain amplifier. But very simple. The gain should be variable with a control voltage. Non-inverting.
    Do you know of one.
    All the Analog devices ones have way more features than we would like

    - - - Updated - - -

    We have a half sine control voltage which we wish to gradually vary the magnitude of. (ie not different discrete switchable gain levels)
    Last edited by treez; 1st September 2019 at 12:34.

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    Re: Variable gain amplifier

    Many possible solutions, different by linearity, noise and drift, bandwidth, accuracy and repeatability. Some specs needed.



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    Re: Variable gain amplifier

    its just the 100Hz half sine reference to a error amplifier of a pfc stage....we need to change its magnitude slowly. from 2v peak to 0v peak



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    Re: Variable gain amplifier

    A light-dependent resistor (usually Cadmium-sulfide cell) is an option.

    A jfet varies its gain as you vary bias voltage. These are less readily available than they used to be.

    Also consider a magnetic amplifier (made from a transformer). Gain is altered by running a DC voltage in one winding, while running the signal through the other winding.



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    Re: Variable gain amplifier

    For these types of uses, a CA3080 would fit the bill. But my understanding is that it is nowadays obsolete.
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  6. #6
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    Re: Variable gain amplifier

    Hi,

    Now we know:
    * 100Hz half sine
    * 2V peak --> 0V peak

    Any trimmer, any pot, any EEpot should do.

    Klaus
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