Current Reference for Pre-regulator Circuit

[rmanalo]

Hello everyone,

I have a question on pre-regulator circuits. Shown below is snipped from Mora's book.



The question is on the generation of the current, Ix.

Here is my block diagram for my circuit.



Which one makes sense or what points do I have to look out for?
The one above is simpler but I doubt if its stable.
The one below is more appropriate I think but I need to make a separate current reference subcircuit.
I'm open to criticism.

Best regards,
rmanalo

 

[dick_freebird]

Work backward from what you hope to achieve.

If your goal is to enhance PSRR (V) and you have a means to
trim the final reference for temp (T) & process (P) then a
simple resistor-fed (for Ix) "preregulator" might do. I like to
add a source-follower buffer, myself, as often the pre-reg
supplies loads besides the Iref/Vref, which could add internal
crosstalk if Zprereg is too high. I also prefer to use stacks
of the same sorts of FETs as what will be powered, for a
bit of poor-boy tracking, rather than PN diodes which don't
bear any relation to anything in CMOS circuits.