BJT Power Loss & Junction Temperature Calculator

This calculator helps you determine if your Bipolar Junction Transistor (BJT) and cooling solution can safely manage the combined heat from the collector-emitter path and the base-drive circuit.

Use this tool to:

  1. Calculate real-time power dissipation, accounting for both Collector-Emitter saturation VCE(sat) and the power required to drive the Base VBE(sat).
  2. Select the correct package or heatsink (e.g., TO-92 for small signals vs. TO-220 for power) to maintain a safe junction temperature.
  3. Identify thermal bottlenecks and evaluate if a higher-gain transistor h(FE) or a MOSFET would be better suited for your thermal requirements.
BJT Input Parameters
Results
Thermal Warning: Junction temperature exceeds 125°C. Lower the current or add a heatsink.

*Calculation: Total Power = (VCE_sat * IC + VBE_sat * (IC/hFE)) * Duty Cycle.

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