**Related Resources: heat transfer**

### Maximum Power Dissipation Transistor Equations and Calculator

**Heat Transfer Engineering**

**Thermodynamics**

**Engineering Physics **

Maximum Power Dissipation of a Transistor Equation and Calculator:

Assumptions:

1 Steady operating conditions exist.

2 The transistor case is isothermal at 85°C.

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Preview: Maximum Power Dissipation of a Transistor Calculator

Rate of heat transfer

Where:

Q = Heat Steady State Transfer (W)

R_{case-ambient} = Rated case-to-ambient thermal resistance (°C/W)

T_{c} = Transistor case temperature (°C)

T_{∞} = Surrounding environment temperature (°C)

The transistor can be used at higher power levels by attaching it to a heat sink (which lowers the thermal resistance by increasing the heat transfer surface area, as discussed in the next example) or by using a fan (which lowers the thermal resistance by increasing the convection heat transfer coefficient).