# 2N4150 Transistor Derating Curves

2N4150 Temperature-Power Derating Curve [2N3419, 2N5237, 2N5238]
NPN Medium Power Switching Silicon Transistor. Package, TO-5 metal Can.
2N4150 Applications; General Purpose, Low power, High voltage.

2N4150 Transistor Operational Power Derating Curve

Use the Curves to determine maximum operational DC power based on operational case temperature, derate power as required. In this particular instance the chart is showing case temperature in still air.
Derating charts will shows one of three cases;
ambient temperature [Ta], case temperature [Tc], or junction temperature [Tj].

How to read the chart; First the maximum possible junction temperature [Tj] is 200C, and should not be exceeded. The right most curve allows the device to operate up to 200C, at zero watts. The other curves provide a more conservative design approach to a maximum of 150C or 125C temperature. The design using a junction temperature of 110C would be the most conservative. Pick a maximum junction temperature [below 200C] and run a line parallel to one of the curves to determine the transistors operating range.

Additional Transistor Derating Curves and graphs
Temperature derating is a standard design practice for electrical engineers.

Refer to MIL-PRF-19500/394; Semiconductor Device, Transistor, NPN, Silicon, Power Switching, Types: 2N4150, 2N5237, 2N5238, 2N4150S, 2N5237S, and 2N5238S, JAN, [TO-5 metal package]

2N4150 Maximum Operational Ratings:
Collector Emitter Voltage = 70 volts dc
Collector Base Voltage = 100 volts dc
Emitter Base Voltage = 10 volts dc
Power Dissipation 250C = 1 Watt
Operating Temperature = -65 to +2000C
Storage Temperature = -65 to +2000C

The collector is internally connected to the case. [TO-5 Package Details].

Guides to high temperature operation of electronic components

These curves all share the same characteristics; that is they start at some normal operating point at 25 degrees centigrade, defined as maximum power rating, which is than reduced at a linear rate down to one of four operating temperatures. The starting power rating is shown as one of four points, which develops into four operating lines. The lowest of the two lines are the regions that most designers should be operating around, however any point under the highest point is possible. The lowest two of the four lines terminate at 110 degrees and 125 degrees centigrade.

The point is that knowing the recommended operating point at dc and the maximum operating temperature, than it's possible to develop a simply derating equation that works just as well as the curves do. The starting operating point is the total power dissipation given in the data sheet as Pt, and normally provided at 25C. The termination point is the maximum desired junction temperature, which could be either 110 or 125C. However the data sheet might provide a junction temperature of 200 degrees, which would be the maximum allowable. Of course when referring to any type of derating, usually a maximum value is not used because the point is to operate below any maximum value.

In any case, the total power dissipation at 25 degrees centigrade sets the x-axis and zero power dissipation at 200 degrees centigrade sets the y-axis. This is how the 'derate linearly' equation comes about in the data sheet, which indicates the identical information that the curves do. However, the difference between the data sheet value and the recommendations found in this section is that the maximum junction temperature of 200C is never used. The normal values of either 110 or 125C are used in this section, which are well below the maximum junction temperature.

The data sheet and the curves provided here both indicate that 200C is the absolute maximum junction temperature. However the difference between the two is that these curves never recommend operating near the maximum junction temperature, while the data sheet provides the derating equation that does derate the device down to the maximum junction operating point. This operating point is always shown as the upper most solid line in the derating curves, but unlike the data sheet the notes clearly indicate never to operate on this particular line. Although not shown above there may be a dashed line above the final maximum curve shown above which indicates thermal runaway.

Editor note; The title of the military document includes power switching, but in this case the term switching does not mean fast switching as it would when used by it self. In this case the term implies that the device is able to switch a high power as compared to other devices. In fact the document does not even give any switching data. Although it does provide a test set-up to measure switching times. In most cases a transistor switching time test set-up is just the transistor, with a minimum number of biasing resistors to configure the operating point. Other than that, the test only defines the rise and fall of the test pulse and the resulting switching times of the output.

The rise and fall times for the 2N4150 is 500nS, which is not considered fast at all. The switching times are based on a Base current of 500mA and a Collector voltage of 5 volts.

Hermetically Sealed TO-5 metal Can

Modified 1/21/12