Transistor Derating Recommendations



Transistor Derating Recommendations based on a linear equation.
Unlike the guidelines in this section, Transistor Derating Curves are not provided.
Most data sheets only provide an equation without a chart.

Transistor Failure Rate, Applied R&M Manual for Defence Systems
Transistor Failure Rate

These design recommendations are for devices in still air, with no other near-by devices generating heat. So the recommendations do not account for a device enclosed in a chassis or next to other transistors on the Printed Wiring Board [PWB]. So in the final design these number may not achieve the design goal of keeping the junction temperature under its maximum number [depending on the individual transistor].
As a general guideline use the Derating Factor shown to the left of the part number.
The derating factor may apply to one or more packages, using the same semiconductor.

2N918, TO-72 metal can, Derate linearly above 25C, 1.14 mW/0C

2N1893, TO-5 metal can, Derate linearly above 25C, 17.2 mW/0C

2N2060, TO-77 metal can, Derate linearly above 25C, 12.1 mW/0C

2N2369, TO-18 metal can, Derate linearly above 25C, 2.06 mW/0C

2N2605, TO-46 metal can, Derate linearly above 25C, 2.28 mW/0C

2N2857, TO-72 metal can, Derate linearly above 25C, 1.71 mW/0C

2N2905, TO-39 metal can, Derate linearly above 25C, 17.2 mW/0C

2N2907, TO-18 metal can, Derate linearly above 25C, 3.08 mW/0C

2N2919, TO-78 metal can, Derate linearly above 25C, 7.14 mW/0C

2N2920, TO-78 metal can, Derate linearly above 25C, 7.14 mW/0C

2N3057, TO-46 metal can, Derate linearly above 25C, 10.3 mW/0C

2N3227, TO-18 metal can, Derate linearly above 25C, 2.06 mW/0C

2N3486, PNP, TO-46 metal can, Derate linearly above 25C, 11.43 mW/0C

2N3499, NPN, TO-39 metal can, Derate linearly above 25C, 5.71 mW/0C

2N3500, NPN, TO-39 metal can, Derate linearly above 25C, 5.71 mW/0C

2N3501, NPN, TO-39 package, Derate linearly above 25C, 5.71 mW/0C

2N3506A, NPN, TO-39 package, Derate linearly above 25C, 28.6 mW/0C

2N3507, NPN, TO-39 package, Derate linearly above 25C, 5.71 mW/0C

2N3700, NPN, TO-18 package, Derate linearly above 25C, 3.08 mW/0C

2N3735, TO-39 metal Can, Derate linearly above 25C, 16.6 mW/C

2N3737, TO-46 metal Can, Derate linearly above 25C, 11.3 mW/C

2N3810, TO-78 metal Can, Derate linearly above 25C, 3.43 mW/C

2N3811, TO-78 metal Can, Derate linearly above 25C, 3.43 mW/C

2N3866, TO-39 metal Can, Derate linearly above 25C, 16.6 mW/C

2N3904, TO-92, SOT-23, SOT-223, Derate linearly above 25C, 5 mW/C

2N3960, TO-18 metal Can, Derate linearly above 25C, 2.3 mW/C

2N3996, Stud-Mount, Derate linearly above 25C, 11.4 mW/C

2N3997, Stud-Mount, Derate linearly above 25C, 11.4 mW/C

2N3998, Bolt-Mount, Derate linearly above 25C, 11.4 mW/C

2N3999, Bolt-Mount, Derate linearly above 25C, 11.4 mW/C

2N4029, TO-18 metal Can, Derate linearly above 37.5C, 3.08 mW/C

2N4449, TBD package, Derate linearly 6.85 mW/0C above TC = +250C

2N6674, 2N6675 TO-3 package, Derate linearly 34.2 mW/0C above TC = +250C

2N6689, 2N6690 TO-61 package, Derate linearly 17.1 mW/0C above TC = +250C

2N7367 IGBT, TO-258 package, Derate linearly 1.56 W/0C above TC = +250C

2N7368 IGBT, TO-259 package, Derate linearly 1.56 W/0C above TC = +250C

2N7508U3, TO-276AA package, Derate linearly 0.6 mW/0C above TC = +250C

2N758xT3, TO-254AA package Derate linearly 1.67 W/0C above TC = +250C
[2N7580T3, 2N7582T3, 2N7584T3, 2N7585T3, & 2N7580T3 in a TO-254AA package].

2N7625T3, TO-257AA package, Derate linearly 0.6 mW/0C above TC = +250C

Attach a Heat Sink to the components tab for higher temperature operation.
Otherwise follow the recommendations in the curve or consult the data sheet.

For a general Rule-of-Thumb recommendation follow this Dearating Factor
Transistor Stress Ratio = Operating Power / Rated Power = 75%.

Engineering best practices indicate that all designs should be derated for temperature.
Which means a design should never force a device to operate at its maximum power dissipation [on near its maximum power dissipation, without leaving some operating room].
A circuit design should also never force a semiconductor to operate at or near its maximum junction temperature.
Pushing the device up to its dissipation limits causes the semiconductor junction to heat up.
The problem is compounded as either the package temperature increases or the surrounding air temperature is increased. In general the life of a component [transistor in this case] reduces as the component temperature is increased [junction temperature].




Transistor Package

Transistor Case Outlines

How to Derate;
2N6546 Derating Guidelines
Derating Components Guidelines
Derating Terms


Related Vendors;
Transistor Manufacturers
Heat Sink Manufacturers

All the equation start at 25 degrees C.
25C is also known as room temperature.




Transistor Derating Factor:
Standard Recommendation:
Derate Power by 50%
Derate current to 75%
Derate applied voltage to 75%




PC motherboard
Home

Distributor rolodex Electronic Components Electronic Equipment EDA CDROM Software Engineering Standards, BOB card Cabled Computer Bus Electronic Engineering Design Table Conversion DB9-to-DB25.
DistributorsComponents Equipment Software Standards Buses Design Reference

Modified 1/16/12
© 1998 - 2016 All rights reserved Larry Davis