Ways to realize a floating current source

[mirror_pole]

Hello guys,

I have a question concerning how to realize a floating current source referring to the following circuit: https://www.semanticscholar.org/pap...dc5e9204b0b80f8d1d6349db65b44964a868/figure/0

Only method i know is to implement them using translinear loops. This seems pretty challenging regarding the low voltage supply of only 1.2V.
I read through all papers concerning this circuit but sadly there is no information regarding this current sources.

Calculation of small signal common mode gain replaces the sources with an intrinsic resistance R.

Maybe someone has a clue?

kind regards

 

[Mahmoud_Sofy]

I think you can still use simple current mirror or wide swing current mirror
the problem is that being floating results in having different source voltage from that source voltage of the mirroring mos in the reference side, so you can, in the reference side, add additional diode-connected mos in the stack before the gnd, so you raise the source voltage of the reference mirroring mos to a higher level like the mos in your circuit. you can find also a smart configuration to track the source voltage level of your mos and hence keeps your mirroring precise

 

[mirror_pole]

Hey Mahmoud_Sofy thanks for your reply. This configuration that u are describing is in fact a similar idea of the translinear loop configuration and actually made me understand it even more now, thanks!
Floating current sources realised by translinear loops do actually the same as u describe, stacking diode connected device under the mirroring transistor to apply "level shift", so the vgs voltages become equal. Of course there is more to it.