Transistor Design Guide Lines
2N4239 Temperature-Power Derating Curve [2N4238, 2N4237]
NPN Low Power Transistor. Package, TO-39.
2N3439 Applications; General Purpose Amplifiers [GP Amps]
2N4239 Temperature-Power Derating Curve
Use the Graph to determine maximum power dissipation of a 2N4239 based on operational ambient temperature. Attaching a heat sink to the metal can will allow the device to operate at a higher temperature with out the need to reduce power consumption. The graph provides maximum power dissipation in still air at the ambient temperature indicated. Applying forced air will also allow greater power dissipation at a given operating temperature. Attaching a heat-sink will also allow better heat convection or radiation into the surrounding air.
Temperature derating is a standard design practice, Transistor Derating Curves.
Refer to MIL-PRF-19500/581; Semiconductor Device, Transistor, NPN, Silicon, Amplifier Types: 2N4237, 2N4238, AND 2N4239. Available in a TO-39 case, or TO-205 case packages.
The components are qualified to JAN, JANTX, AND JANTXV when following this military specification, or purchasing to the DOD part number.
2N4239 Maximum Ratings, 250C:
Collector Emitter Voltage = 80 volts dc [Vceo]
Collector Base Voltage = 100 volts dc [Vcbo]
Emitter Base Voltage = 6 volts dc [Vebo]
Power Dissipation = 1 Watt, 250C [Ta, ambient temperature]
Power Dissipation = 6.0 Watt, 250C [Tc, case temperature]
Operating Junction Temperature = -65 to +2000C [Tj]
Storage Temperature = -65 to +2000C [Tstg]
Complementary Device; 2N4236 PNP Transistor
2N4239 Derating Curve Notes:
Top curve is thermal runaway loci and cannot be used as a derate design curve since it exceeds
the maximum ratings for this part. Operating under this curve using these mounting conditions assures the
device will not have a thermal runaway. This is the true inverse of the worst case thermal resistance value
extrapolated out to the thermal runaway point.
Thermal Runaway is a condition that occurs when power losses within the device cause additional heat to build causing more heat to be generate, increasing the power losses until the junction temperature is exceeded resulting in the destruction of the 2N4239 transistor.
The leads of the TO-39 package of the 2N4239 may be used to conduct heat away from the metal can. Use the shortest leads possible and solder the component leads into a large copper pad to dissipate the heat into the printed wiring board and away from the junction of the 2N4239.
TO-39 metal Can Transistor Dearting by Case temperature
Engineering notation; Although it might seem like a good idea to use a derating curve developed for one transistor for another similar one, it's would not be good design process. The structure and layout of the semiconductor die might be different, or the actual physical size of the die might be different. The manufacturing process between the two different transistors could be different. The placement of the bonding wires on the semiconductor die could be in different places and so on. The best course of action is to revert to what ever company wide derating factor is being used and implement that into any design calculations. For example; if the process indicates that the transistors characteristics should be derated by 70 percent of maximum, than that is what should be used. Never operate a transistor, or any device, to its maximum limits, it's just not good design practice. Note that this curve, and others on this site do cover more than one transistor part number, but it should not be inferred that they cover any similar item.
