2N5581 Transistor Derating Guide Curve

2N5581 Temperature-Power Derating Curve [2N5582]
NPN Switching Transistor. Package, TO-46 [TO-206-AB].

Temperature Derating Graph for a 2N5581 and 2N5582 Transistor
2N5581 Temperature Derating Curve [2N5582 Transistor]

Use the Graph to determine the required 2N5581 power derating [wattage] based on operating ambient temperature. The maximum wattage of 3 watts is available at 250C and begins to fall off above 300C in still air.
The graph only relates to the 2N5581 [or 2N5582], there are no other devices near by that could generate additional heat. In a real design the circuit board will contain components that are also generating heat which are not accounted for in the graph.
Instead of the graph the 2N5581 / 2N5582 transistor may also be derated using an equation:
Derate linearly 2.86mW/C for ambient temperatures [Ta] above 25C.
Derate linearly 11.43mW/C for case temperatures [Tc] above 25C.
Additional Transistor Derating Curves for other devices.
Temperature derating is a common design practice in circuit design, and may be mandatory depending on the organization controlling or over seeing the design.

2N5581 Maximum Operation Ratings:
Collector Emitter Voltage = 50 volts
Collector Base Voltage = 75 volts
Emitter Base Voltage = 6.0 volts
Power Dissipation 250C = 3.0 Watts
2N5581 Operating Temperature = -65 to +2000C
The 2N5582 has about the same electrical characteristics as the 2N5581, but with a higher Hfe [which also effect the switching time].

Both the 2N5581 and 2N5582 have the same switching times. The Turn-On time is defined as 35nS and the Turn-Off time is defined as 300nS. Switching times is an important characteristic when the transistors are specified as switching transistors. The turn-on time is measured from 10 percent of the input rise time to 90 percent of the output fall time [10 percent of the rise time [of the input voltage] to 90 percent of the fall time, or 10 percent or the output voltage].

Refer to MIL-PRF-19500/423; Semiconductor Device, Transistor, NPN, Silicon, Switching, Type 2N5581 and 2N5582, JAN, JANTX, and JANTXV, [TO-46]

Listing of Transistor Manufacturers and BJT vendors

Lead Identification for a TO-46 Transistor Case
TO-46 Package drawing

Pinout Designations;;
Lead 1 Emitter,
Lead 2 Base,
Lead 3 Collector.
Case is electrically connected to Lead 3.

Specification for Semiconductor Devices

Test Methods for Semiconductor Devices

How to Derate;
General Derating Guidelines

PC motherboard

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Modified 12/30/11
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