noise noise noise ......

[chacha]

iam doing a folded mixer and an amplifier preceding to it.
this gain stage is just a differential amplifier with a resistor in place of current bias transistor. (if i use a current bias then noise figure is too big..)

I did pnoise analysis(using spectreRF).

In the noise report it is saying that the one of the input transistors is generating 85% of the noise and the other is generating only 5% of the total noise. this is looking very strange and confusing me.

can any one explain this???

 

[khouly]

can u send the schmatic , and just remark on it the transistors u r talking about

kouly

 

[chacha]

i have attached the schematic with this reply.

Added after 10 minutes:

i have added the schematic...

 

[chacha]

iam attaching the folded mixer and highlighing the main contributor for the noise.
this mainly flicker noise.
i have also attached the gain stage in the prevoius reply.

noise figure( mixer+gain stage) = 39db
noise figure(mixer) = 33db


if i dont use the transistor highlighted and using the ideal current source( from analogLib) then the results are as follows.

noise figure(mixer+gain stage) = 38db
noise figure(mixer) = 18db.

my spec for the noise figure is (including the gain stage ) is 17db.

i am facing a serious problem with this noise.
i desperately need some valuable suggestions in this regard.

THANK YOU.........