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newhand
Joined: 07 Dec 2004
Posts: 33
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 04 Feb 2007 13:45 About noise cancellation |
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hi guys:
Now I am designing an opamp in continuous time which requires a SNR>=90db using the smic .13 process(seems poor process).As the VP_P of the input signal is 1V,to achieve the SNR specification,I need to control the Equivalent Output Noise(Vn)<=11uV.
But according from the simulation data,I find the Vn>=100uV(It seems 1/f noise Dominate in 20-20kHz),how can I decrease the noise,could someone offer some paper about this,thanks~~
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Humungus
Joined: 10 Jul 2001
Posts: 432
Helped: 26
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04 Feb 2007 18:42 Re: About noise cancellation |
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| to reduce 1/f noise you need to increase the current and the size of transistors
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xjxmn
Joined: 31 Jan 2007
Posts: 27
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05 Feb 2007 2:57 About noise cancellation |
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Which frequency range do you care?
I think you need to control the Equivalent intput Noise (RMS) to <=11uV, not output noise.
Large input transistor size, or chopper.
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bbbb
Joined: 24 Apr 2006
Posts: 47
Helped: 11
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05 Feb 2007 20:48 About noise cancellation |
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I think in general there are 3 solutions for the problem:
1. Circuit optimization (increasing gm and WL product)
2. chopper amplfier
3. Topolgies that are offset insensitive. Many of offset reduction techniques also reduce the flicker noise
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05 Feb 2007 20:48 Ads |
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newhand
Joined: 07 Dec 2004
Posts: 33
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06 Feb 2007 17:23 About noise cancellation |
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Thanks above.
Now I have read some paper about the 1/f noise cancellation.It seems a good choice to use chopper amplifier,i see some paper of chopping in the instrument amp whoise frequency is very low.
As My opamp is used in the audio codec(mp3),so my care freq is 20-20kHz,I am not sure whether the chopping technich is still effective in this range?
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wonbef
Joined: 13 Oct 2004
Posts: 191
Helped: 3
Location: Nanshan, Shenzhen
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07 Feb 2007 8:17 About noise cancellation |
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| can use cascaded structure?
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betty1007
Joined: 15 Jan 2007
Posts: 50
Helped: 2
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11 Feb 2007 0:00 About noise cancellation |
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| larger dimension input transistor, small dimension load transistor
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