Electrical

Constant Current Source with BJT and Zener

Electrical Diagrams · made in Skemio

Ladder schematic showing 12V DC driving a Zener bias rung and an active collector load rung monitored with an ammeter.
Ladder schematic showing 12V DC driving a Zener bias rung and an active collector load rung monitored with an ammeter.
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What it shows

  • A Zener diode holds the BJT base at a constant reference voltage.
  • Emitter voltage equals Vz minus Vbe, fixing current through Re.
  • Collector current mirrors emitter current independent of load R.

The takeaway

Lock the emitter voltage to keep current steady across shifting load impedances.

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