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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