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" The Rohm 6.2V should be fine. I never simulated the temp performance, that was MindSim." I was going to ask you both when the design is firmed up, to hit it with a heat gun and watch/record the

Peter, 1) Well, I don't have an enviro chamber either..... in fact I don't even have a breadboard!? :-) 2) I thought the 2sk3563's had finally worked ok in earlier versions? 3) Best I found:

Roger: I don't have an environmental chamber at home, I only have a hair dryer!. I didnt temperature test. I did cobble the circuit using three 5.1V zeners( I did pick up the 6.2V Rohm zeners but

I began some temperature testing simulations and the On Semi 6.2V Zeners I originally used only exhibited about half the expected tempco in simulation. I don't know why.....? I changed them over to

Roger: Interesting. You used 6.1~ 6.2 V zeners to compensate for a tr junction. A long long time ago, in a distant design lab I didn't use zeners for compensation, In some circuits that had dc, we

The Rohm 6.2V should be fine. I never simulated the temp performance, that was MindSim. Generally, in what we usually call Zener Diodes, the are actually two breakdown mechanisms: Zener breakdown and

Peter, That last "Way-Improved" circuit is working extremely well, I encourage you to try it. You do not have to have all three zeners to get functionality, you merely adjust the bottom trim resistor

Roger: The closest mosfet in my Micro-Cap library was a 2SK311 to the 2SK3563 that I was proto-typing with. Since these mosfets are much higher current parts, than those you may have used in your

Actually, the original values are working quite well, with only the 2.85Meg resistor being trimmed for nominal RegHV value.

Peter, If you decide to try this Way-Improved Cascoded Shunt Regulator, I will suggest the following, same circuit as before but with resistor-value changes. BTW, by taking the voltage to the

OK, found it. Interesting....... Mindsim tells me that doing that will reduce the feedback regulation of the voltage by essentially reducing the forward gain of the "opamp." By the "opamp," I mean the

Roger Please see the attachment in message #299 After my boo-boo, which caused the voltage to sag, it was feedback. So I changed the amount of feedback until the voltage would not rise or fall much. I

So, I eluded below to the fact that changing current in the Zener(s) is the remaining dominant error in regulation over voltage. So check out the enclosed circuit and regulation curve..... Probably

1) I don't understand, can you post a schematic? 2) In the earlier current mirror configuration, the only purpose of the diode-connected BJT is to drop one Vbe so that the voltage on the resistor

Roger: Couple morning questions: 1) any comments of using two resistors for the dropper and taking the mid point connections to feed the bias resistor string ? I found that it greatly reduces any

Attached is a simulated performance curve for the Darlington BJT Cascoded HV Regulator. As you can see, when UnRegHV goes from 1000V to 1200V, the RegHV output goes from 904V to 918V. I think that is

of course you can use any zener to cobble it up for functionality, and adjust the bottom resistor for correct output. 6.3V zener is just for the tempco. rogerw -- This email has been checked for

Roger: Thank you again. Of course i will give this latest circuit a try. Hopefully, nothing exciting will happen this weekend, so I can tinker away. I don't have any 6.3V zeners handy at home. I will

Before you quit try the enclosed version. In simulation the single BJT base current was biggest circuit error left. Darlington pair simulated and regulated quite well. Two 6.3V zeners at +2mV/degC

Roger: Micro-cap sim doesn't look that good but on the proto board it works well. Put two 5.1V zeners in series. Used two resistors for the dropper to get some negative feedback. Seems to regulate