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As far as I know abt the Flicker noise you can not eliminate it when you are operating at low frequencies on any semiconductor devices. Even its orgin is clear till date.There is a way to reduce by using PMOS instead of NMOS whwereever possible. And thrmal noise is present always you have no way to eliminate it except to increse your SNR to decresde the BER.
Added after 1 minutes:
I am wrong in my reply that the origin is not clear for Flicker noise.
Flicker noise seems due to random trapping/detrapping of carriers near the Si/SiO2 interface. But the subject is still under active discussion.
Thermal noise origin is the same as for resistor: random movement of cariers due to thermal excitation.
As to suppress them:
- Flicker noise can be reduced in low frequency circuits (like audio) by using double sampling or chopping. See the excellent article by Enz and Temes 'Circuit techniques for reducing the effects of op-amp imperfections: autozeroing, correlated double sampling, and chopper stabilization'
- For thermal noise, you need to reduce it by circuit design consideration (as said by gunturikishore you need to increase the SNR)
Hopes it helps
regards
As I said in my previous reply Flicker Noise is inevitable in any semiconductor device. But the advantage with it is that you can neglect this noise safely at higher frequencies may be above 10 K Hz. Being Flicker Noise proportinal to the 1/freq
its noise is considerable at low frequency. This is highly significant and can not be neglected at base band frequencies.
Themal Noise is due the random motion of the electrons in any material above absolute (not centigrade) zero temperature. THis is almost same at any frequency and its noise depends on the Bandwidth of the system under consideration. You can refer any Communication or Solid State Devices book for these noises.
It is hard to eliminate the flicker noise in low frequency applications. But some people believe that PMOS has lower flicker noise than NMOS. As the transistor dimension decreasing, this advantage of PMOS become not so obvious.
if u r using a NMOS diff amp then noise figure can be improved by having PMOS diff amp on top of NMOS with same cascode structure. Noise is inherent in all systems. we can only try to reduce it
Definately going for a very big transistor area can reduce the flicker noise. But, do not blindly do so. Thermal noise is reduced by higher gm when referred to the input. So, the key for Low noise design is to go for big widths and modest lengths.
i do not agree with going for very big transistor, it's actually harmful for a low noise circuit since u r more susceptible to noise coupling now. How big is very big?
Flicker noise although looks like a low frequency phenomenon,it's one of the major source of noise in High frequency applications .In RF Applications one can see large Area for the input transistor's .Any insights into Kick back noise if the area of the mosfet is large ??
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