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About noise cancellation

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newhand

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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~~:cry:
 

to reduce 1/f noise you need to increase the current and the size of transistors
 

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.
 

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
 

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?
 

larger dimension input transistor, small dimension load transistor
 

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