Power supply for voltage references

[iMo]

..
The main function of R3（R5 inrevised sch ） is to offload a portion of the thermal load from the L7805. Assuming the FPGA/MCU current consumption is 30mA, the voltage drop across the 100-ohm resistor will be 3V. This reduces the voltage drop across the L7805, preventing heat dissipation from being concentrated solely on the L7805. I've changed the resistor package to 1206.

I would put there a 3.2V zener as the serial voltage dropper (HP does it in its high end meters, for example). But wired after that CLC low pass (like the R7 is wired)..

[aronake]

One idea:

On the AC side, start with one DP-241-5-120 transformer to go from 220V to 120V, then one DP-241-5-12 (with primary in parallel) to go from 120V to 12.6V AC, then a linear regulator to 12V or what voltage may be wanted.

Idea then that there are two transformers in series that each help to reduce lekage.

The DP-241-5-12 transformer is the one Marco Reps tested for leakage here:
https://youtu.be/9JinSfCKuNQ?si=DwPtIN2V676FicvO&t=565

https://www.belfuse.com/media/datasheets/products/transformers/ds-st-241-series.pdf