..he doesn't work here any more.
If it were my decision, I would *not* use this circuit, but we are a million miles behind schedule, and the boss is asking us to define exactly what is the risk of this circuit...as a respin of the PCB will delay us and infuriate our customer.
I mean, its one of those "weird" circuits that I would never ever have done....so I am not sure how to exactly quantify the exact risk....does any reader know?
There are two electrical people in the company..... the senior engineer and me...the senior engineer just wants to keep shipping it as it is, since he reckons we'll get away with it, after all, a few prototypes worked fine on the bench, or so he said, I only just joined this company a few days ago.
I actually believe that the operation of this PNP transistor, with Ib a lot greater than Ic, is a weird operation, and probably none of the datasheet parameters apply..do you agree?
I don't think any single engineer can be expected to understand PNP operation when its hooked up in such a weird way.....I didn't think power current was supposed to go through the BE diode?....I thought the BE diode was for small control current only?.....I suspect that the datasheet value of 600mA for the BE current refers only to a short transient current of 600mA? (since the CPH3105 datasheet does say its for 'switching' operation)...maybe they are thinking the CPH3105 would normally be used to turn a mosfet ON , and the 600mA would only flow at turn ON time...for a short interval...who knows?, the datasheet doesn't really say.
I'll own up now and say I have never before seen a BJT being used with the power current going through the BE junction...i thought BE junctions were delicate little blossoms that we should be careful with?