2N5151 Transistor Derating Curve

2N5151 Temperature-Power Derating Curve [2N5153]
PNP Switching Transistor. Package, [TO-205].
2N5151 Applications; High-speed switching

2N5151 Transistor Temperature-Power Derating Curves

Derate the 2N5151 by 5.7mW/⁰C above an ambient temperature of 25⁰C
The derating curve applies to a 2N5153 PNP transistor as well.

The derating curve details the maximum allowable power dissipation with ambient temperature, although in this case the chart specifies case temperature. Maximum operational power dissipation is achievable at 25⁰C [or below]. However above 25C the maximum package dissipation must be reduce to insure that the devices junction temperature remains constant.
The chart shows the desired power rating where most users want to limit junction temperature in their application, which are depicted by the lines that terminate at 110C and 125C.

Heat Sink;
Installing a [clip-on] heat-sink is one method of insuring that the device will operate above the ambient temperature depicted in the curves. Decreasing a components operational limits as temperature is increased is called derating.
Air Flow issues;
Implementing forced air cooling will also allow the 2N5151 to operate higher that the graph represents, as the power derating curves are for free-air. Free-Air or still-air is air surrounding the device that is not forced [via a fan] or inhibited because the device in placed within a chassis [enclosure] or case.
Altitude issues;
An additional power reduction must also be accounted for if the device is operated above sea-level. Check the manufacturers data sheet for operation above the altitude of 10,000 feet [or above sea-level].
Heat Sources;
Insure that there are no adjacent heat sources which may be producing radiant heat, the graph does not account for heat produced from other sources.

Refer to MIL-PRF-19500/545; Silicon PNP Power Semiconductor Device, Transistor types; 2N5151, 2N5153, 2N5151L, 2N5153L, 2N5151U3, and 2N5153U3, meeting the following DOD qualification levels; JAN, JANTX, JANS, JANHC, and JANKC qualified parts [TO-39 metal Can]. The U3 suffix is the surface mount version.
Note; links to the alternate surface mount packages to the left.
The 2N5151 is available in a TO-205 package [metal can], Similar to a TO-39.

Ambient temperature. is the air temperature measured below a semiconductor device, in an environment of substantially uniform temperature, cooled only by natural air convection [free-air], and not materially affected by reflective and radiant surfaces [adjacent devices].

Case temperature. is that temperature measured at a specified point on the case of a semiconductor device. Note that the curves shown above relate to the 2N5151's case temperature

Storage temperature [Tstg]. Storage temperature is a temperature at which the device may be stored without any power being applied. Storage temperature for the 2N5151 transistor ranges between -65 to +200⁰C.