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    virtual short op amp

    i am electrical engg. i am new to this op-amp world. i would like to know what exactly a VIRTUAL GROUND refer to........


    thanks

    •   Alt20th June 2006, 08:47

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    meaning of virtual ground in op amp

    I/p impedance of an opamp is very high and hence very little current flows thru it's inputs and hence very little voltage drop occurs at i/p.Hence if one of it's i/p is grounded ,since voltage difference b/w two i/ps will be very less we can assume other one of the i/p also to be at ground and hence giving rise o term 'virtual gound'.



    •   Alt20th June 2006, 09:19

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    virtual ground in OP AMP

    virtual ground ... there r two inputs to an Opamp now
    whatever voltage is present at 1 input ...same is assumed to present at 2nd input too!
    this concept is very vital ..



    •   Alt20th June 2006, 10:22

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    Re: virtual ground in OP AMP

    Similar explenations you can find in the Wikipedia:
    http://en.wikipedia.org/wiki/Virtual_ground

    In general, the concept of "virtual ground" has wider meaning than the above ..
    Sometimes it is called a "rail splitter": it splits a single supply in two, so you have two "voltage rails" plus "new" ground - the virtual ground ..
    Here you will find more:
    http://tangentsoft.net/elec/vgrounds.html

    Regards,
    IanP



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    virtual ground in OP AMP

    Ideal opamp gain is high. It makes the two input equal.If one input is connected to ground,the other is virtual ground



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    Re: virtual ground in OP AMP

    due to -ve feedback the -ve terminal approaches the +ve terminal since the gain of opamp is in 1000's .we say the -ve terminal of opamp is at virtual gnd (virtual since not really grounded)if +ve terminal is at gnd.


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    Re: virtual ground in OP AMP

    The op-amp has two input terminals. When the op-amp is used with some negative feedback around it, the two input terminals are at same potential [ideally], although they are physically not connected together. This is referred to as VIRTUAL SHORT [and NOT virtual ground]. In case one of the terminal is kept at GROUND Potential, then the other one is also at GROUND Potential. This can be referred to as VIRTUAL GROUND.



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    Re: virtual ground in OP AMP

    Both the inverting and non inverting inputs of an opamp are bootstrapped to each other. If one is set to a certian voltage the other input will follow......



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