2N6300 Transistor Derating Curve

2N6300 Temperature-Power Derating Curve [2N6301]
NPN Medium Power Darlington Transistor. Package, TO-66 metal Can.

2N6300 Derating Curve, Maximum Operation

Use the Graph to determine how much to derate power [wattage] based on operational case temperature [in still air]. See other Transistor Derating Curves.
The above chart details the maximum allowable power dissipation with increasing ambient temperature. Maximum operational power dissipation is achievable at 25⁰C. 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. The two lowest curves is the area that most users should limit their designs to. The uppermost curve shows the maximum semiconductor junction temperature that should not be exceeded. In fact the maximum junction temperature should not even be approached in normal operation when the guideline to use the lower most power rating lines are implemented.

Decreasing a devices operational limits as temperature is increased is called derating, in this case derating a devices operational power dissipation vs increasing ambient temperature.

Refer to MIL-PRF-19500/539; Semiconductor Device, NPN Power Darlington Transistor; Types 2N6300 and 2N6301, JAN, JANTX, and JANTXV, [TO-66]

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 (example: TO-66). The Collector of this device is directly connected to the case or body of the metal package. [Derating Definitions, bottom of page]. Refer to FR4 Thermal Impedance Chart for an understanding of how a PCB conducts heat.

The 2N6300 and 2N6301 are Darlington transistors. A Darlington transistor as shown is basically two transistors connected as a dual Emitter amplifier in order to increase gain. So by definition the package needs to contain two transistors. What is not so common is the addition of the protection diode on the output of the second transistor. Although many FET package also use a diode connected in this fashion. Even less common is the introduction of two Base Emitter shunt resistors.

2N6300 Schematic