2N3055 Transistor Derating Curve

2N3055 Temperature-Power Derating Curve and linearly equation.
NPN Power Transistor. Package, TO-3 metal diamond shape package.
2N3055 Applications; General-purpose switching, power amplifiers and audio amplifier.

2N3055 Temperature-Power Derating Curve for Case Temperature
2N3055 Transistor Operational Power Derating Curve

Derate the power dissipation for the 2N3055 by 0.657 W/0C for any operating temperature above 250C. No power reduction is required for temperatures below 25C. Some vendors may provide a much stricter derating, as this MIL Spec indicates 34.2mW/C for temperatures over 25C.

Use the curve to determine the amount of power [wattage] derating based on case temperature [operational ambient temperature]. Because the collector is connected to the case the device may be directly attached to a heat sink to allow higher temperature operation. Extrusion heat-sinks are by far the most common for power amplifiers, and allow the formation of elaborate two-dimensional shapes capable of dissipating large heat loads. Refer below for a graphic of one style of heat sink. The two styles of heat sinks for a 2N3055 include Rectangular Shape, or Diamond Shape.

Note that the curves indicate Case Temperature [Tc] and applies to free-air [still-air]. Fans may be used to induce forced air cooling which will greatly enhance operation over higher temperatures. In any case for longest life use either of the gray curves.
Sockets are available for a TO-3 package, but should only be used during design and testing. Example socket; 0804MC [8-pin TO-3 socket].
Temperature derating is a standard practice for engineers during circuit design. Use any of the three lower curves in the graph above, or select a line parallel to one of the curves. The highest curve to the right represents the maximum operating temperature of the 2N3055 and should not be used in the design [but as a guide].

Refer to MIL-PRF-19500/407; Silicon Semiconductor Device, NPN Power Transistor, Types covered: 2N3055, JAN, JANTX, and JANTXV, [TO-3 metal case]. Also seen as a TO-204AA case, depending on the vendor or OEM.

2N3055 Maximum Operational Ratings:
Collector Emitter Voltage = 70 volts dc [Vceo]
Collector Base Voltage = 100 volts dc [Vcbo]
Emitter Base Voltage = 10 volts dc [Vebo]
Collector Current = 15 Amps dc [Ic]
Base Current = 7 Amps dc [Ic]
Current Gain = 20 to 70, Ic =4A, Vce = 4V [hfe]
Maximum Operating Frequency = 3 MHz
Power Dissipation 250C = 6 Watt [Pt]
Operating Temperature, Junction = -65 to +2000C [Tj]
Storage Temperature = -65 to +2000C [Tstg]

TO-3 Pin Out: Lead 1 = emitter, lead 2 = base, lead 3 = collector.
The collector is electrically connected to the case.

The Lead-Free [Pb-Free] version is 2N3055G in a TO-204AA metal package. [RoHS]

Refer to; MIL-PRF-19500; Semiconductor Devices, General Specification

2N3055 Derating Definitions

Case mount. [Diamond Shape Flange Mount] A type of package outline or case style which provides a method of readily attaching one surface of the semiconductor device to a larger heat dissipater to achieve thermal management of the case temperature. The 2N3055 package may also be called a diamond style package. Note the large cut-outs in the heat sink for terminals 1 and 2 of the 2N3055 transistor. Another heatsink is shown above.

TO-3 Transistor Heat Sink with metal Fins, including cut-outs for the terminals
TO-3 Heat Sink

Case temperature. Case temperature is that temperature measured at a specified point on the case of a 2N3055 semiconductor device. The location should be specified by JEDEC, because the temperature will change based on the location of the Thermocouple. The military specification that defines how to derate the 2N3055 does not define the location of the temperature probe. So it has to be assumed to be the location of the measurement is defined by JEDEC, although that assumption could change the over-all results. The 2N3055 is a two-terminal device, the collector forms the case of the device. Some data sheets or derating curves may use the case temperature of a 2N3055 while other data sheets may use the ambient temperature around the 2N3055. The top curve in the graph is the maximum junction temperature, which is normally always shown in any of the derating graphs.

Ambient temperature. Ambient temperature is the air temperature measured below a semiconductor device, in an environment of substantially uniform temperature, cooled only by natural air convection [Free-Air], and not materially affected by reflective and radiant surfaces [no other near-by devices generating heat]. Note that the air temperature is normally be assumed to be the surrounding temperature as found in what ever chassis the 2N3055 is installed in. Testing, however would require a more definitive measurement. The equation that determines the derating of the 2N3055 transistor in ambient air is given by: decrease by 34.2mW/C for ambient temperatures over 25 degrees centigrade. The derating equation and curve imply that no device is radiating heat toward the 2N3055, and that the device is not installed with an enclosure that inhibits air flow. Also not stated, the Power Dissipation curve works at sea-level, a higher altitude may required tighter derating.

Diamond shape package

2N3055 Board Mount Heat Sink with large metal fins
2N3055 Heatsink

TO-3 Package Drawing and Lead Identification
TO-3 metal Can

Guidelines to;
Derating Electronic Components
Transistor Derating Curves
NPN BJT Derating Curves
TO-3 Package [Physical Dimensions]
TO-204 Package [Physical Dimensions]

Device Vendors;
Transistor Manufacturers [BJTs]
Heat Sink Manufacturers

2N3055 Similar versions;
2N3054 is the low power version
2N2955 is a compliment PNP version
MJ2955 is a PNP version
Component cost; $1 per 2N3055

2N3055 Manufacturers;
ON Semiconductor

2N3055 Transistor packaged in a TO-3 Case
2N3055 BJT

Drawing of a Diamond shape TO-3 2N3055 Transistor
2N3055 Case Package

Reliability is based on junction temperature.
Derating increases reliability by lowering Tj.
Design the 2N3055 at the lowest Tj possible.
Exceeding the max Tj 2N3055 results in failure.
Burn-Out and Failure mean the same thing.

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Modified 6/13/15
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