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From: Winfield Hill
Subject: Re: Rail to Rail Limit
Date: 28 Sep 2002 05:12:00 -0700
Organization: Rowland Institute
X-Newsreader: Direct Read News 2.98
Kevin McMurtrie wrote...
> Winfield Hill wrote:
>> John Woodgate wrote...
>>> Winfield Hill wrote
>>>> John Woodgate wrote...
>>>>> I bet his 100 mV is an r.m.s value, and he wants a gain of 25
>>>>> applied to it. That's a peak-to-peak output voltage of 7 volts!
>>>>> NO WAY with a 3V supply.
>>>> It can be done, I know a way, but not with a rail-rail opamp. :-)
>>> Indeed. One could get 7kV p-p with enough winding skill. (;-)
>> Nope, no inductors or transformers required. :-)
> Do you mean bootstrapping an op-amp chip to 7kV? You're probably the
> only guy on Earth who has to test his op-amp circuits while wearing
> goggles. Hell, at 7kV you'd have to bootstrap a shield over the
> op-amp to keep coronas from blowing the inputs.
Hah, 7kV was John's number. But I do routinely run FET opamps at 3kV.
This is the rated channeltron voltage; channeltrons have weak current
outputs needing a sensitive trans-resistance stage before presentation
to an isolation amplifier. Some of the 3kV wiring joints are coated
with the old classic red anti-cornona dope.
Although I don't wear goggles while testing at rated voltage, it comes
in handy that I've reached the age where I'm always wearing glasses,
and they act as an instant shield for all sorts of things, like flying
snips of wire, etc. I also keep one hand behind my back during high-
voltage testing. This limits shock damage to a little skin burn or a
nice black hole in the finger. :-)
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