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I have gotten this wrong, PNPs are ON when the base is pulled LOW.
Also I need to reorient the diagram with the +12v on a common bus. . .
First of all, I'll assume the system voltage is 14v.
R2 and R3 form a voltage divider. output voltage =(R3/(R2+R3))* input voltage
13.8= 1000/(10+1000) * 14 --so Vee is 13.8v. (that is the voltage present at the emitters of the PNPs)
OK, Loren said Q1 is a voltage regulator. That looks like an "emitter follower" circuit, with the output above the emitter, at terminal 1 of the meter movement (makes sense as the meter movement is what gets driven) and the voltage input on the base, collector to ground. In normal operation Q1 is in cutoff, it's only when the base gets pulled low
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Last edited by 304065; 06-24-2008 at 12:02 PM..
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