2N2222 Temperature-Power Derating Curve
NPN General Purpose Silicon Transistor. Package, TO-18 metal Can.
Temperature Derating Curve for 2N2222A Transistor, TO-18 Case
2N2222 Derating
Use the Graph to determine how much to derate power [wattage] based on ambient operational temperature of a 2N2222A in a TO-18 package. The derating graph uses a TO-18 metal can with 0.125 inch leads. Much of the heat conducted away from the 2N2222 metal can is via the leads into the printed wiring board, so it's important to keep the leads as short as possible while still keeping the body of the 2N2222 from resting on the PWB. Note that the terminal lead length is provided on the derating chart, implying a maximum length.
The inclusion of heat sinks is never given in transistor derating curves, because of the vast number of different types and differnt mounting options. However because the collector of the transistor is attached to the case, a heat sink is a good option for a TO-18 package.
Additional Transistor Derating Curves for other transistor types.
Note that the maximum operating temperature in free air [still air] is 2000C, but at zero power dissipation [maximum junction temperature]. Applying forced air to the system via a Fan, or installing a Heat-Sink to the metal can will allow the 2N2222 to operate at a higher temperature at a given current draw.
Refer to MIL-PRF-19500/255 Silicon NPN Transistor Switching Semiconductor Device, Types: 2N2221A, 2N2221AL, 2N2222A, 2N2222AL, 2N2221AUA, 2N2222AUA, 2N2221AUB, 2N2222AUB, 2N2221AUBC, and 2N2222AUBC, JAN qualified, [TO-18]
2N2222A Maximum Operational Ratings
Collector Emitter Voltage = 50 volts dc
Collector Base Voltage = 75 volts dc
Emitter Base Voltage = 6 volts dc
Power Dissipation 250C = 500mW
Collector Current = 800mA dc at 50V [Vceo]
Gain = 20 to 300 depending on colelctor current
Operating Temperature = -65 to +2000C [maximum operational temperature]
Check the 2N2222 Data sheet for additional parameters.
Listing of Transistor Manufacturers [BJTs and FETs]
Additional Guidelines for Derating Electronic Components, by component type.
Design advice; With out a heat sink and operating in still air much of the heat generated by the 2N2222 will be transferred from the semiconductor to the component terminals via conduction. Insure that the traces running to the transistor leads are wide traces, especially to the collector terminal, to transfer heat away from the semiconductor. Of course short traces are always a good idea.
2N2222 Availability
The 2N2222 transistor is a general purpose device manufactured by a number of different companies. One such manufacturer is STMicroelectronics, although there are a number of companies that produce the 2N2222 in the cheaper plastic TO-92 package. Although the plastic package would have a completely different derating curve than the one shown above for the metal package.
