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Newbie : Microprocessor A/D question


Tim Jenkins

Jan 1, 1970

I'm looking at an existing circuit trying to understand how it is built to
further my electronics knowledge. There is a part of the circuit thats
puzzling me though.

The circuit has a 6502 microprocessor on board. One of the standard I/O
ports on the micro is connected to the Base of a BC212 transistor via a 10K
resistor. The collector of the BC212 is connected to the supply rail (+12v)
and the emitter is connected back to the Microprocessor's VREF pin for the
onboard A/D converter.

Do you think this is so the supply to the VREF can be controlled by the
Micro ? To conserve power maybe ? (The circuit is battery powered).