Low current increase the noise

[bicave]

When reading a document, it say that
" low current increase the noise" ? I don;t know the reason and
what else effect to the noise.

 

[naalald]

Hi,
Of course it depends on the circuit. But in SC circuits as current decreases you should decrease the capacitor value to maintain the speed. So, the KT/C noise increases.

 

[A.Anand Srinivasan]

maybe the author would have talked about the noise to signal ratio....
it would be better if you quote the whole text or mention the book and page number...

 

[kobeghost]

for the thermal noise I think it will decrease with the current decrease,considering its key factor Gm.as for the 1/f noise,it is determined by the WL

 

[tia_design]

It depends, for CMOS op amp, high current for input pair will reduce the noise, oh, what I said is not correct. Increasing current of input pair will increase both thermal noise and Gm, but for thermal noise, its gain is increased by √2, while for signal, the gain is increased by 2. Compare with each other, the noise is reduced. We often talk about input referred noise

 

[lladnar23]

That's right -- in terms of thermal noise, you typically have to burn 4x the power to get a 2x improvement in SNR

 

[A.Anand Srinivasan]

That's right -- in terms of thermal noise, you typically have to burn 4x the power to get a 2x improvement in SNR

can you please brief what you mean by that... which power r u talking about increasing to increase the SNR....

 

[alasliu]

input pairs thermal noise is 4kTr/gm. so if you increase current, gm ascend. thermal noise will be reduced.

 

[leo_o2]

It is 4KT(2/3gm) for MOSFET.