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dave cox · 21st Jul 2020, 3:30 pm

I think I3 should be about 9K ?

EDIT
Ooops 9K it too high ...
You need to get something like 2mA down each leg of the LTP when the regulator is regulating !
R6 will have ~0.7V across so R=0.7V/2mA so 330R or 390R - ish

'I3' - this has the zener voltage at one end (eg 30V) and the reference voltage (plus a BE junction) at the other and should give 4mA
30V-(2V5+0V7) = 26V8 the R=26V8/4mA so R ~ 6K8 (not 9K although it would probably work)

dc

21st Jul 2020, 3:30 pm	#51
dave cox Nonode Join Date: Jan 2009 Location: Bristol, UK. Posts: 2,061	Re: High voltage regulator circuit. I think I3 should be about 9K ? EDIT Ooops 9K it too high ... You need to get something like 2mA down each leg of the LTP when the regulator is regulating ! R6 will have ~0.7V across so R=0.7V/2mA so 330R or 390R - ish 'I3' - this has the zener voltage at one end (eg 30V) and the reference voltage (plus a BE junction) at the other and should give 4mA 30V-(2V5+0V7) = 26V8 the R=26V8/4mA so R ~ 6K8 (not 9K although it would probably work) dc Last edited by dave cox; 21st Jul 2020 at 3:51 pm.