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"However there might be some advantage of a Series Pass with the photomultiplier detector bias ring which requires HV dc current? rogerw" Well the PMT resistor string does require a certain amount of

Now that I think about it some more, I think all the tube shunt regulators (or replaced with diode string) have a "dropping resistor" from the UnRegHV and then followed by another high value, say 1Meg

there would need to be a series resistor, say 1Meg, after the series pass regulator low impedance output (well only kinda low) and going to a GM tube. That kinda points out that this is not practical

Q: what happens when the GM tube fires, essentially going to ground? Geo To: "CDV700CLUB" <[email protected]> Sent: Sunday, April 3, 2022 7:40:32 AM Subject: Re: [CDV700CLUB] Question and an

Peter, The reason I ask is that this Shunt Regulator can be turned quite easily into a Series Pass Regulator such that the "dropping resistor" can become, say 10Meg and the bias currents to the

In LTSpice, it is not a model for any actual Jfet, it is just an ideal Jfet model with no breakdown. I simulated the characteristic curve, such as Id vs Vds for Vgs= 5V just like a curve tracer would

Roger: PMT resistor divider resistance is all over the place. The lowest I encountered was a commercially made socket for Hamamatsu R647 pmt, and its total resistance was about 3.3 M ohms.The pmt base

Roger: Out of curiosity what generic JFET did you use ? I am not familiar with high voltage JFETs. I've only used JFETs rated for 100V or less. Michael: Happy to pass to prototyping torch to you! I

Michael, Great, I look forward to hearing results from your effort! I also bought some of the depletion mode devices, to breadboard with when I can get around to it. Peter, You mentioned that your

Roger / Peter I have ordered a few of each type of MOSFET I have some 5.1v and 15v zeners to try in place of the 6.2v Will try your 'improved' circuit and report back mje

Michael, My goodness, you are good at finding these things! I think that device will also work fine. Again, I have already simulated a generic JFet for the cascodes, which is naturally a depletion

Roger - thank you for the confirmation If depletion mode will work the there is the LND150N3-G lots in stock at $0.57 each

All, Here is the current state of my self-styled "Way-Improved" version in simulation. That simulation result below is never varying more than about < +/-3V over temp and UnRegHV from 1000V to 1200V

Michael, ?That VN0550N3-G looks to be perfectly suited, thanks! Looks like they only have 28 in stock presently, better make your purchase! I may order a few too but I will wait till you and Peter

Roger / Peter I have been following this thread with much interest. Thank you I looked for low current MOSFETs and found this one that is through hole and affordable : VN0550N3-G? $1.75 each

Notice that Bss126 is a depletion mode, not enhancement mode, but does not matter hardly at all in this circuit. It only means Vgs will be negative, not positive. In fact, that realization has spurred

Roger Good morning. The Infineon BSS126 is a nice? 600V part. Thanks. It bugs me that? these parts are not cheap, all the stores really mark up the prices or tack on some expensive shipping. My

Peter, Here is a HV n-ch MosFet? that looks very promising: https://static6.arrow.com/aropdfconversion/63454afd4a5cd81607a68c1d9d1470f986aaac5d/infineon-bss126i-datasheet-v02_01-en.pdf If it can be

Right, understood sim. Geo To: "CDV700CLUB" <[email protected]> Sent: Saturday, April 2, 2022 8:56:38 AM Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and

Geo, I have now simulated the latest version I am playing with over temp from -25degC to 75degC. It did NOT temp compensate well (the 3Vbe + 3Vz scheme) with the 6.2V OnSemi Zeners, but when I