[Diy_efi] Driving injector: forward biased diode between B and C of NPN

[Perry Harrington]

Are you sure that you're EBC is correctly notated?  I would say it's a
flyback zener without personally inspecting the circuit or seing pics.

--Perry

On Mon, Aug 05, 2002 at 01:55:36AM -0400, Stephen Webb wrote:
> 
> I'm getting my hands a bit dirty trying to reverse-engineer an injector
> driver circuit.  The box is actually a K-jetronic control unit from a VW
> which drives a "frequency valve", which is more or less a fuel injector.
> 
> One side of the injector is always hot, the other side is switched with
> what appears to be an NPN transistor, though I could be wrong on that
> (couldn't find a listing for the part numbers)  The markings are:
> 
> PH ON588  m8827
> 
> For now I am going to assume it's an NPN transistor.  Everything about how
> it's connected makes sense to me except for a diode which is connected
> from the base to the collector.  
> 
> Could someone explain what this diode does?  
> 
> I'm stepping outside of my normal area of expertise on this, so if this is
> basic stuff, I apologize.  From reading TAOE I gather that a reverse
> biased diode across an inductive load may be expected (there isn't one,
> though there is a 10 ohm, 10 watt+ resistor in series).  Also there is
> mention of a base-emitter diode, but I haven't been able to find anything
> on a base-collector diode.  
> 
> 
> TIA
> 
> -Steve
> 
> 
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-- 
Perry Harrington			Data Acquisition & Instrumentation, Inc	
perry at dainst dot com					 http://www.dainst.com/

Those who would give up essential liberty to purchase a little temporary safety
deserve neither liberty or safety. Nor, are they likely to end up with either.
                             -- Benjamin Franklin

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