PNP BJT current source – Bipolar Junction Transistor – 2N3906

Current source made by a PNP bipolar junction transistor (BJT) is just like one made with a NPN BJT, but with opposite polarities.

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PNP BJT current source trimpot controlled demo circuit 2N3906 PNP Bipolar junction transistor schematic diagram by electronzap electronzapdotcom
PNP BJT current source trimpot controlled demo circuit 2N3906 PNP Bipolar junction transistor schematic diagram by electronzap electronzapdotcom
2N3906 PNP bipolar junction transistor BJT schematic symbol and pin layout diagram by electronzap electronzapdotcom
2N3906 PNP bipolar junction transistor BJT schematic symbol and pin layout diagram by electronzap electronzapdotcom

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:
Simple pnp bipolar junction transistor BJT current source set by trimpot voltage divider circuit by electronzap electronzapdotcom
Simple pnp bipolar junction transistor BJT current source set by trimpot voltage divider circuit by electronzap electronzapdotcom

2N3906 PNP BJT current source set with trimpot voltage divider circuit build by electronzap

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