DIY injector cleaning
Bruce Bowling
bowling at cebaf.gov
Fri Dec 5 17:39:22 GMT 1997
>
> then, there's VBE and VEB. VBE is the BE diode forward voltage.
> It's "typically" .7 volts, though it'll more than likely be closer
> to 1 volt. (If the 330 ohm resistor were not present, the 555 would
> be essentially driving a 1 volt short circuit.) Then, VEB. This
> is the BE diode reverse voltage. Not looking at the TIP120 data,
> but I can tell you that few BJT's have over 6 to 10 volts reverse
> voltage rating. But, this circuit has no negative voltage, so the
> VEB rating should not be exceeded (he'd have to worry if he had
> a speedup cap or an inductor in the base circuit).
You are probably right. I read the blister pack, at 2:30 AM, and saw
the rating under the "absolute maximum", and I interpreted it as
the maximum base-emitter voltage, but was probably the reverse voltage.
>
> One last question -- why doesn't he use a switching, logic MOSFET ?
>
>
I chose to use the TIP120, mainly because it is widely available at the shack.
Power logic MOSFET would also work.
> - Bruce
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Bruce A. Bowling
Staff Scientist
Thomas Jefferson National Accelerator Facility
12000 Jefferson Ave - Newport News, VA 23606
(804) 249-7240
bowling at cebaf.gov http://devserve.cebaf.gov/~bowling
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