Here is a simple point to point soldered cascoded MOSFET CCS using the classic DN2540. A very simple design: carbon grid 1K resistors and two potentiometers I had at hand: 2K (coarse) + 100Ω (fine). I can set the operating point of the valve under test from 3mA to 100mA. The anode output is directly coupled to a BNC connector which is hooked to the Pete Millett’s interface. No capacitor used as the interface has a DC blocking capacitor.
I used an old aluminium box and build this takes less than 30min!
