The circuit is from the manual of the integrated circuit used in the excitation of power transistors. The 30 V symmetrical supply should have a few amps of capacity.
This digital potentiometer is from a 1993 publication, but it can be easily assembled today. R1 to...
Maxim MAX16813B 4 Channel LED Driver These Maxim Integrated LED drivers are available from Mouser...
This circuit was found in an American magazine 73 for radio amateurs of the 80s. It is an...