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Alles Gute
Joined: 04 Dec 2003
Posts: 142
Helped: 5
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 05 May 2005 11:35 Bandwidth and Gain Bandwidth |
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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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bastos4321
Joined: 01 Jan 1970
Posts: 341
Helped: 24
Location: space
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05 May 2005 12:02 Re: Bandwidth and Gain Bandwidth |
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| Alles Gute wrote: |
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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yibinhsieh
Joined: 25 Apr 2005
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06 May 2005 14:40 Re: Bandwidth and Gain Bandwidth |
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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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chinito
Joined: 05 Jul 2004
Posts: 133
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07 May 2005 1:22 Re: Bandwidth and Gain Bandwidth |
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| 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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Alles Gute
Joined: 04 Dec 2003
Posts: 142
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07 May 2005 10:32 Re: Bandwidth and Gain Bandwidth |
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| yibinhsieh wrote: |
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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yibinhsieh
Joined: 25 Apr 2005
Posts: 196
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07 May 2005 11:03 Re: Bandwidth and Gain Bandwidth |
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Alles Gute wrote
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That means wide band aplifier is just used in open loop configuration, never used in closed loop?
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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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zhi_yi
Joined: 02 Feb 2005
Posts: 197
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07 May 2005 13:01 Re: Bandwidth and Gain Bandwidth |
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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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alski
Joined: 13 Mar 2005
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amarnath
Joined: 24 Apr 2003
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08 May 2005 4:12 Bandwidth and Gain Bandwidth |
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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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Borber
Joined: 01 Jan 1970
Posts: 1561
Helped: 117
Location: Slovenia
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08 May 2005 5:27 Re: Bandwidth and Gain Bandwidth |
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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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layes2
Joined: 03 Dec 2004
Posts: 346
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19 May 2005 6:21 Re: Bandwidth and Gain Bandwidth |
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bandwidth usually -3db one
gainBW is unitybandwith
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Georgy
Joined: 20 May 2005
Posts: 5
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20 May 2005 11:34 Bandwidth and Gain Bandwidth |
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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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20 May 2005 11:34 Ads |
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nemoium
Joined: 19 Aug 2004
Posts: 4
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21 May 2005 13:36 Bandwidth and Gain Bandwidth |
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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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drasta
Joined: 15 Sep 2004
Posts: 26
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23 May 2005 11:06 Re: Bandwidth and Gain Bandwidth |
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| Usually it means large GBW because you need high gain in large BW.
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sreechoudhary
Joined: 02 Dec 2004
Posts: 32
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23 May 2005 16:07 Bandwidth and Gain Bandwidth |
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bandwith refers to -3dbone
where as gain bandwith is unity band (power and current)
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