Current source made by a PNP bipolar junction transistor (BJT) is just like one made with a NPN BJT, but with opposite polarities.
The voltage at the emitter will be the base voltage plus about 0.6V in relationship to ground due to the base-emitter diode shift. The difference between the positive supply voltage and the emitter voltage will be the voltage across the emitter resistor.
The voltage across the emitter resistor divided by it’s resistance (I=V/R) will be the current through the resistor, collector to emitter, and any load from collector to ground.
The collector load will not determine the current as long as there is enough supply voltage to power everything.
Bonus diagram and video:
- 555 Timer IC This particulars of this integrated circuit covered on this page make a lot more sense after you study the basic circuits that follow.
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