Thanks Greg and John. That is very interesting about the isolated DCDC converters.
I've been trying to get the simulator in KiCAD 5.x nightlies to simulate some of these circuits, but no luck so far. I might give LTSpice a try. I've tried out a few variations on the constant current source theme (and there are many more to go from the suggestions on this thread). The latest one I tried was a current *source *version of a temperature stabilized current *sink *as described here <http://www.radio-electronics.com/info/circuits/transistor/active-constant-current-source.php>. I'm not entirely convinced that I translated it from a sink to a source correctly, however it works, except that it is no more stable than the basic constant current source in my first post! Perhaps because the first version is operating well within its parameters anyway, or the NPN isn't really much of a match for the PNP? Anyhow, I would be grateful if you could tell me if I at least got the principle right, or just messed up badly! (BTW, I'm very grateful for your input, but I also don't want to be a pain, but I assume that some other people might find this stuff useful too!). <https://lh3.googleusercontent.com/-t2uZfu_DdYI/WOBStN9V7PI/AAAAAAAAAh8/EawxeyG2uQMnkyYkHfCfk-fZDoYNH8RaQCLcB/s1600/TCCCS.JPG> I also tried this current mirror, which was a complete disaster - BY my calculations, the current should have been limited to about 0.5mA (200/390K), but it grew rapidly to about 30mA before I managed to break the connection, I don't really understand why. But now I do understand why there is no Re in those mirrors - Vb in the equations in my first post is equal to k (i.e. Vbe) so the value for Re is always zero? <https://lh3.googleusercontent.com/-sigis2hjekU/WOBYch_E1UI/AAAAAAAAAiM/tZM6Ttrodoc_r28a6IeNkrEOe-1Px72ggCLcB/s1600/CM.JPG> Again, many thanks for all of your input. I'm going to try the current limiter that Tomasz suggested earlier next. Then on to PMOS. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/3624e9c5-4517-4bba-8993-301d79ea5fad%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
