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    Bandwidth and Gain Bandwidth

    In analog IC, Bandwidth(BW) and Gain Bandwidth(GBW) are the two often seen parameters. BW=-3dB frequency and GBW=Gain*BW.

    When people say "Wide band amplifier". Do they mean large BW or large GBW?

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    Re: Bandwidth and Gain Bandwidth

    Quote Originally Posted by Alles Gute
    In analog IC, Bandwidth(BW) and Gain Bandwidth(GBW) are the two often seen parameters. BW=-3dB frequency and GBW=Gain*BW.

    When people say "Wide band amplifier". Do they mean large BW or large GBW?
    Usually is related to amplifiers and the used terminology is GBW to disting "wide band amplifier".

    Bastos



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    Re: Bandwidth and Gain Bandwidth

    Usually I state the wide bandwidth VGA is for -3dB Bw. Gain-bandwidth product is for OP because it is used in closed loop.

    Yibin.



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    Re: Bandwidth and Gain Bandwidth

    Gain Bandwidth is used more because it is a closed loop concept for amplifiers. Open loop bandwidth is not that important.



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    Re: Bandwidth and Gain Bandwidth

    Quote Originally Posted by yibinhsieh
    Usually I state the wide bandwidth VGA is for -3dB Bw. Gain-bandwidth product is for OP because it is used in closed loop.

    Yibin.
    That means wide band aplifier is just used in open loop configuration, never used in closed loop?



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    Re: Bandwidth and Gain Bandwidth

    Alles Gute wrote

    That means wide band aplifier is just used in open loop configuration, never used in closed loop?
    The wideband 3dB BW amplifier is used in open loop.

    The wide gain-bandwidth product amplifier is used in close loop. Like op used in high-speed ADC. It need GHz gain-bandwidth product amplifiers.

    Yibin.



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    Re: Bandwidth and Gain Bandwidth

    what is an open loop amplifier? and what is a close loop amplifier? can you give me an example please? and then what is the gain bandwidth, is it the range that the gain will not affected by the frequency? and then what is a wide band amplifier?
    please tell me >_<

    thanks for the answer ^^



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    Re: Bandwidth and Gain Bandwidth

    Wikipedia has pretty good explainations on basic operational amplier loop gain and bandwidth. Check out
    http://en.wikipedia.org/wiki/Operational_amplifier.



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    Bandwidth and Gain Bandwidth

    open loop amplifier is that in which there is no feedback.usually the bandwidth of open loop amplifiers is very low(eg opamp 741).in order to make an amplifier usable for practical purposes ,it needs to be used in closed loop mode,which is essentially negative feedback.when u use negative feedback it means that u are willing to sacrifice a portion of the gain of your amplifier for the sake of improved bw,noise performance ,input resistance and o/p resistance etc.i suggest u refer to integrated electronics by millman and halkias for further information.

    regards
    amatnath



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    Re: Bandwidth and Gain Bandwidth

    Bandwidth is -3dB point of frequency characteristics. It is valid for any amplifier is it open loop or closed loop, it does not matter. Gain-bandwidth product is parameter of amplifiers which can be used in closed loop configuration like OPA. This parameter says that higher gain will produce lower -3dB upper frequency limit because GBW is constant. Each amplifier has it's own BGW parameter. Greater GBW means that bandwidth is greater at same gain.
    Wide band amplifier term is used if the bandwidth of amplifier covers all the frequency band of interest. It is used at low pass type of frequency characteristics so as with band pass. It covers wider frequency band than it is needed for particular frequency spectrum of signal.



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    Re: Bandwidth and Gain Bandwidth

    bandwidth usually -3db one

    gainBW is unitybandwith



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    Bandwidth and Gain Bandwidth

    Hi gentlemans! More actual question is where is table with extremal parametres: GBW, power supply, Settling Time and so on. Any like Ginnes Book?
    Note: Sometimes great GBW or BW no enough. Settling Time is very important parametr, it determine yoir ability produse large amplitudes at HFl Bandwidth.



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  13. #13
    nemoium
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    Bandwidth and Gain Bandwidth

    The GBW is a very important concept in the filter design.
    the typical OP gain A have the follow equation:

    A(s)= ωg/(s + ω3db)
    where ωg is the GBW, ωg=A0*ω3db
    A0 is the DC gain.



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    Re: Bandwidth and Gain Bandwidth

    Usually it means large GBW because you need high gain in large BW.



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    Bandwidth and Gain Bandwidth

    bandwith refers to -3dbone
    where as gain bandwith is unity band (power and current)



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