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OCD-D-101-A.? A couple of High Range Tubes for a good price.? Just in time for Puttie Bear or NK to get froggy. Mike L. 304426217251

" However engineering economics and "good enough" motivated Peter to step back to the simpler circuit." Yes that's always the last thing we do here, with an eye on reducing parts count for reliability

Geo, Depending on the output resistance of the BJT at high voltages (a number found in the datasheet or? with a curve tracer) performance might suffer w/o the cascode. This is because, in addition to

" (If you had a 1000V BJT you would not need the cascodes for mere functionality.) rogerw" Yep, that's been the dilemma?here, trying to find a way to transfer the stable "Variable Zener" LM317

Vz is a voltage reference input to a feedback amplifer connected as a voltage gain set by feedback resistor ratio. It is in fact a positive gain opamp configuration as I showed. You can change the

Geo, Now, for your last question below, the answer is yes, you can replace the BJT with just the HV Mosfet and the circuit will function. In fact that is exactly Peter's original circuit, well

Roger. try going directly to the homepage of the group, [ mailto:[email protected] | [email protected] ] Geo To: "CDV700CLUB" <[email protected]> Sent: Tuesday, April 5, 2022 7:04:22 AM

yes that helps a lot. What is the function of V(sub)Z in determining the output V? If the divider variable resistor is locked at a certain value, what effect does changing the Zener have on the

Where do I find the message number of a message? That does not apparently deliver to my email client s/w? rogerw -- This email has been checked for

Geo, Take a look at Peter's simpler schematic he just posted yesterday, and ignore the cascode MosFet, since its main function is to pass the BJT collector current up to the high voltage levels.

Really the question is, skip being variable right now for a moment, what function does the transistor play and ultimately, could you theoretically use a zener on the gate(? or where?) of the FET

Peter and Roger, P. your hand drawn schematic helps me understand more about this. Here's my question, with either or all of these circuits, what happens if the divider string is fixed, even if it has

very kewl! Sorry I have been unresponsive this evening, been visiting with an old hunting buddy. rogerw -- This email has been checked for viruses

Roger: Back to the circuit you posted in message #300 Simple cascode, with only 1 npn tr + 2 mosfets. Since I found the 2SK3265, I removed the 2nd mosfet so its a very basic circuit. 66Meg, two 1 Meg,

Roger: I don't know the details of the avalanche process, but at low low currents ie uA's, is the temperature coefficient predictable ? Also is the avalanche voltage knee stable ? in other words, so

I have always run at least 10uA or so but in my latest circuit sim, I am running only about 4uA. Seems to work in sim-world. Of course they are spec'd with 10mA or more........ So naturally they are

Another good question Peter, we need to know that.Over last weekend I learned that it doesn't take much to make them work. Even 1G Ohm draws them to their rated drop Voltage... 11 G Ohms didn't.Geo

All good points Roger and right on the button.I don't have a 6993, but do have a 719, which looks the same but is 2 or more times longer. Will try it today If possible, otherwise tomorrow for sure.

Roger et al: Please refresh my mind. what sort of current was flowing through the zener(s) ? P

Geo, I would look forward to the same measurement but taken on a 6993 operating at 900V. Maybe operates different from the Russkie's tube, or maybe not..... I totally agree,wrt similarity of your