AoE x-Chapters, floating high-voltage current sources

Here's another section from our new soon-to-printed AoE x-Chapters book: Floating high-voltage current sources.

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This one is 12 pages long, and rather detailed. Paul complained that I was going on and on, but agreed, and helped in the end. Here's my defense, from the text, midway though the saga,

"Why all the fuss? At this point the reader can be excused for wondering why they are being dragged through so many circuits? Why not just show the best HV current-source circuit, and leave it at that? Well, as in engineering

applications will be fine with simple circuits, but others require more effort. The story of improving HV current- source performance is the story of adding more and more

enjoy exploring the options (as we did, designing them!) as we continue with higher-voltage, higher-current versions."

That gave us leave to add five more pages of intense detail.

Floating current source circuits are much more complex than ones that operate off a rail, but they have the advantage they can be used from either end, either as a current source, or as a sink. And available HV parts are not well suited for making non-floating circuits, tied to the HV rail.

Our new x-Chapters book is filled with Pearls of Electronics, as our editor likes to say; a wide assortment of detailed discussions of esoteric engineering circuit-design topics. Not everyone will want to read it straight through, but when you are confronted with a tough design problem, we may have already explored it. Others will read it as an idea generator. Some will enjoy the circuit-design exploration. It's filled with detailed advanced material, not available elsewhere. This 12-page section can serve as an example.

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 Thanks, 
    - Win
Reply to
Winfield Hill
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For a truly floating true current source, I'm fond of PV optocouplers. Only good for 10s of uA. PVs and mosfets can be interesting together.

I'll read it straight through!

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
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Reply to
John Larkin

I believe you can make a variation of the sources on p. 202 with a tube, with the right triode you can have supplies up to a couple kV with the SS regulator safely wrapped up in the grid -> cathode differential.

Might be amusing to add for, ah, "completeness"

Reply to
bitrex

Yes, I thought about that, remembering your and other's proclivity. But we had to draw the line someplace. We used PVs for a floating switch, Figure 3.107, page 205.

Have fun, and don't choke!

--
 Thanks, 
    - Win
Reply to
Winfield Hill

Yes, or up to 20kV, 15A (pulsed) with a 5D21 tube.

--
 Thanks, 
    - Win
Reply to
Winfield Hill

Maybe I'm missing something, but in figure 3x.61D, wouldn't U1 be better used with the adjust pin connected to the Q1 emitter, rather than the base?

Reply to
whit3rd

All the mosfets in that chapter are drawn using a non-standard symbol. In other chapters you have used the interanationally recognized symbol of 50+ years which shows the channel diode on the substrate opposing the gate.

The non-standard symbol can cause confusion as it appears to show a bjt-like emitter structure in the source connection.

piglet

Reply to
piglet

Yes, excellent observation. I'll add this text:

"____ suggested moving U1's adjust pin to Q1's emitter, in Figure 3x.61D. This is a good idea (although U1 is a slow part, Q1's cascode response is fast), possibly as good or better than 3x.61E."

--
 Thanks, 
    - Win
Reply to
Winfield Hill

Corrected this to, "better than 3x.61F"

--
 Thanks, 
    - Win
Reply to
Winfield Hill

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