# What is thermal resistance?

Latest Updated:12/01/2011

## Question:

What is thermal resistance?

Thermal resistance indicates how difficult it is for heat to be transmitted, and is expressed by the package's rising temperature per unit power (see Thermal Design).
Unless otherwise specified, the chip's (PN) junction temperature (Tj) is the maximum storage temperature (125°C for an operational amplifier or comparator).
The thermal resistance from the junction to the package ambient air (Rth: j - A) is calculated as follows from the absolute maximum ratings in the data sheet.

Note that thermal conduction appears like the figure below when changed to an electrical equivalence circuit.

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