PNP Bipolar Junction Transistor BJT Current Source Circuit

Zener diode setting PNP BJT current source 2N3906 bipolar junction transistor schematic diagram by electronzap
Zener diode setting PNP BJT current source 2N3906 bipolar junction transistor schematic diagram by electronzap

Voltage across PNP Bipolar Junction Transistor BJT emitter resistor is approx. 0.6V less than the base voltage in relationship to the positive supply voltage.

The current through the resistor will be the voltage across it, divided by the resistor’s resistance. In the diagram, that is 5V/510Ω = 0.0098…A – rounded off to 0.01A (10mA).

The PNP BJT emitter and collector, are in series with the resistor. So, that current will also flow from the collector to ground.

Current through series components is the same through all of them.

A load between collector to ground will pass the same current as long as there is enough supply voltage to provide the power to do so. That’s why the supply voltage needs to be a fair amount higher than the voltage set across the resistor.

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