Hi all,

I was wondering if anyone here could point me to any good references for the (low to high frequency band) noise analysis of a super-source follower ? I am using a super-source follower as the input or reference stage of a current-mirror and was trying to figure out the simplest way to characterize its noise performance from DC to sub-GHz frequency ranges.

Any comments or inputs are greatly appreciated!

cheers,
sandman.

hi Jerry,

The concept is simple and uses negative feedback on a transistor to reduce its output impedance to the a small factor of the inverse of feedback trans-conductance. I found this link that might explain the circuit in some more detail -http://users.ece.gatech.edu/pallen/Academic/ECE_6412/Spring_2004/L290-ReturnRati... (ref. page 6).

This finds typical use in LDO's but I am trying to use this in the reference stage of simple current mirriror.. and then analyse its noise performance at DC to some hundreds-of-megahertz. Any suggestions?

cheers,

hi Raja,

Thanks for your inputs. I will need to dig into the LDO references but I remember several papers on this. I will have to come back to you on this.

I am in fact not using this for my LDO, but rather as an input stage for a current mirror operating from DC to several 100's of MHz. I use the low impedance of the super-source follower as the input, so in effect, I am trying to calculate the noise performance referred back to the Base, as a voltage noise source (in series with the Base of the main transistor)! The schematic is exactly as in the link I mentioned above.

Do you think you could share your derivations here? That would be interesting.

cheers,