2N6249 Transistor Derating Curve

2N6249 Temperature-Power Derating Curve
NPN Power Transistor. Package, TO-3 metal Can [TO-254AA, TO-257AA].
2N6249 applications; High voltage inverters, Switching regulators, Amplifiers

2N6249 Transistor Temperature-Power Derating Curve

The chart details the maximum allowable DC power dissipation with increasing case temperature. Maximum operational power dissipation is achievable at 25C. However above 25C the maximum package dissipation, or power, must be reduce to insure that the devices junction temperature remains constant. The higher the ambient temperature is increased the lower the allowable power dissipation, as depicted in the curves. Decreasing a devices operational limits as temperature is increased is called derating, in this case derating a devices operational power dissipation vs increasing ambient [surrounding] temperature. The graph above depicts the derating of a 2N6249 transistor in a TO-254AA package or TO-3 package.

Attaching the device to a heat sink will allow for higher operating temperatures with the same power dissipation. The TO-3 is a Case Mount package and may be attached directly to a heat sink. The TO-254 is a Tab Mount package which allows for the attachment of a heat sink to the metal tab.
Use the leads of either package to assist in conducting heat away from the component body, use larger than needed copper pads on the circuit board as a heat sink. The TO-3 package is normally mounted very near the circuit board,; however the TO-254 may not so make its leads as short as possible. For additional board data, refer to FR4 Thermal Impedance Chart; which provides thermal impedance data based on the weight [thickness] of the copper.

Additional Transistor Derating Curves for other devices.
How to read the derating curves; Transistor Derating Curve Interpretation
Temperature derating is a standard design practice for electrical engineers.

Refer to MIL-PRF-19500/510; Semiconductor Device, Transistor, NPN, Silicon, Power, Types 2N6249, 2N6249T1, 2N6249T3, 2N6250, 2N6250T1, 2N6250T3, 2N6251, 2N6251T1, 2N6251T3, JAN, JANTX, JANTXV, AND JANS, JANHC, and JANKC [TO-3, TO-257AA, TO-254AA]

2N6249 Maximum Ratings 25⁰C [Operational]:
Collector Emitter Voltage = 200 volts dc
Collector Base Voltage = 300 volts dc
Emitter Base Voltage = 6.0 volts dc
Power Dissipation 25⁰C = 6 Watts
Operating Temperature = -65 to +200⁰C
Storage Temperature = -65 to +200⁰C

TO-254 Terminals: Lead 1, Base. Lead 2, Collector. Lead 3, Emitter
TO-257 Terminals: Lead 1, Base. Lead 2, Collector. Lead 3, Emitter
Cases TO-254 and TO-257 appear the same but have different physical dimensions.

Case mount. A type of package which provides a method of readily attaching one surface of the semiconductor device to a heat dissipater to achieve thermal management of the case temperature. The TO-3 is a case mount device.
Case temperature. The temperature measured at a specified point on the case of a semiconductor device.