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Re: O-Scope for tesla coil use



Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Stork,

I think you mean like this:

http://hot-streamer.com/temp/DiffProbe01.gif

See the files at:

http://hot-streamer.com/temp

Starting with "diffprobe".

Protecting the scope from faults is a big deal. See this one which is more safe:

http://hot-streamer.com/temp/DiffProbe03.gif

http://hot-streamer.com/temp/DiffProbe21.gif

I would not bother trying to use other than a simple battery powered low bandwidth TL082 circuit. I did manage to get the fast TI chip to sort of work but it was a real mess. Not worth it... Best to keep it simple.

The problem is the high impedances at high voltage and high bandwidth require compensations circuits that normal humans just can't figure out. If it was easy, Tek would not get $1000+ for the darn things... There are nice high sped op amps out there, but soldering in countless little 1pF chips all over the place to pull the signals in is just about impossible. You pretty much need the Tek probe to guide you anyway. Then, the next time you try it everything is different so you start from scratch again. Not repeatable at all... So if the simple TL082 one will work, your all set, if you need like 50MHz stuff, you just have to buy the darn things.

Cheers,

        Terry


At 10:56 AM 3/23/2005, you wrote:
Terry,

Back in 2003 you had a thread going about a differential wideband HF amplifier based on the TL082 quad Jfet op-amp. I remember Malcolm responding. I cannot find the thread now though. How did the project turn out? Do you have a design/schematic?

A plug in differential amp for older tube scopes is cheaper, but confined to that tube scope. A stand alone fet differential amp is much more versatile, but much more $$$.

I have long felt a stand alone fet differental op-amp PCB would be a good project. Maybe I can revive it.

Our higher voltage DC voltage regulator PCB is progressing. Hopefully, I'll be able to post the schematic.

stork