2N4238 Temperature-Power Derating Curve [2N4237, 2N4239]
NPN Low Power Transistor. Package, TO-39.
2N3438 Applications; General Purpose Amplifiers [GP Amps]
2N4238 Temperature-Power Derating Curve
Use the Graph to determine 2N4238 power dissipation 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.
Transistor Derating Curves
Temperature derating is a standard design practice for electrical engineers.
Derating a transistor insures that the junction temperature never exceeds its maximum rating.
Refer to MIL-PRF-19500/581B; Semiconductor Device, Transistor, NPN, Silicon, Amplifier Types: 2N4237, 2N4238, AND 2N4239, JAN, JANTX, AND JANTXV, [TO-39]
2N4238 Maximum Ratings: at 250C
Collector Emitter Voltage = 60 volts dc [Vceo]
Collector Base Voltage = 80 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; 2N4235 PNP Transistor
2N4238 Derating Curve Notes:
The top curve is thermal runaway loci and cannot be used as a derate design curve since it exceeds
the maximum ratings for this part [dashed line]. 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.
The curve to the left represents the maximum possible operating curve without exceeding the permissible 200C junction temperature. The best design uses the curve that terminates at 100C. However; pick the desired junction temperature [under 200C] are draw a line parallel to one of the curse to determine the operating region of the device [2N4238].
DEPARTMENT OF DEFENSE SPECIFICATIONS
MIL-PRF-19500 - Semiconductor Devices, General Specification for.
DEPARTMENT OF DEFENSE STANDARDS
MIL-STD-750 - Test Methods for Semiconductor Devices.
