Dual regulators for single rail?

[leadbelly]

Any comments on the attached schematic? It seems to me that this design would better reject common mode noise in the AC, but I don't know enough to be sure. I don't remember ever seeing such a scheme shown in a schematic, but I don't know if that means it's pointless or if that as parts count go up, a designer will forgo a 3 terminal regulator in favour of discrete components.

 

[leadbelly]

Anybody? Bueller? Bueller?

 

[leadbelly]

Seriously, nobody has a comment or opinion?

 

[richie00boy]

I think there's no need, the transformer galvanic isolation provides the rejection of common-mode noise from the mains. All you are doing there is doubling the supply impedance and creating twice as much heat, real estate and cost.

 

[tINY]

Common mode noise should be pretty much eliminated by the transformer. For non-CM noise, I don't believe this circuit buys you anything either.

Is there some issue you are trying to solve here?




-tINY

 

[EWorkshop1708]

It's a split power supply without using the middle rail as ground.

Maybe it can be used to get a higher voltage with lower voltage regulators?

 

[leadbelly]

Is there some issue you are trying to solve here?

Not an issue, no. I am planning to build a phono preamp with poor PSRR and want the best performance regulator I can get without going to a discrete design.

 

[richie00boy]

Forget using 78xx or 79xx regs then. Check out the low noise applications on the LM317 datasheet.