2N6691 Transistor Derating Curve

2N6691 Temperature-Power Derating Curve
NPN High Power Transistor. Package, TO-61.
2N6691 Applications; High power switching, power amplifier

2N6691 Case Temperature-Power Derating Curve
2N6691 Temperature Derating Curve

The chart indicates the maximum power dissipation with increasing component case temperature. Maximum operational power dissipation is achievable at 25C. However above 25C the maximum package dissipation, or power, must be reduce to insure that the devices junction temperature remains constant. The higher the ambient temperature is increased the lower the allowable power dissipation, as depicted in the curves.
Derating is the method of decreasing a devices operational limits as temperature is increased, in this case derating a devices operational power dissipation vs increasing case temperature. This particular graph depicts the derating of a 2N6691 and 2N6693 transistor in a TO-61 package. Additional Transistor Derating Curves, for other transistor types.

When using the chart, pick one of the curves or a maximum junction temperature [which is the same thing] and run a line parallel to it to determine the devices operational range. The curve terminating at 200C represents the maximum operating limits, not to exceed. The curve terminating at 110C represents the most conservative operating limits, and should be selected if possible. Other wise the 125C curve should be used as good design practice.

Refer to MIL-PRF-19500/538D; Semiconductor Device, Transistor, NPN, Silicon, Power, Types 2N6676, 2N6678, 2N6676T1, 2N6678T1, 2N6676T3, 2N6678T3, 2N6691, and 2N6693 [TO-61 outline]. Some of these transistors use different packages, and may use a different derating graph than the one shown above.

2N6691 Maximum Operation Ratings:
Collector Emitter Voltage = 300 volts dc
Emitter Base Voltage = 8.0 volts dc
Power Dissipation 250C = 175 Watts
Operating Temperature = -65 to +2000C
Storage Temperature = -65 to +2000C

Pinout note; Terminal 1 Emitter, Terminal 2 Base, Terminal 3 Collector.
The Case is isolated from terminal leads and used for mounting and heat dissipation.

Related Devices:
2N6676 Derating Curve, which also covers derating the 2N6676T1, and 2N6676T3 components. Each of these components use the same semiconductor but use a different component package.

Case mount. A type of package which provides a method of readily attaching one surface of the semiconductor device to a heat dissipater to achieve thermal management of the case temperature. The TO-61 uses a blot to mount the device
Case temperature. Case temperature is that temperature measured at a specified point on the case of a semiconductor device [Tc].

Bolt style package mounting

TO-61 package drawing
TO-61 Package

How to Derate;
Derating Components Guidelines

Related Topics;
Transistor Manufacturers, BJT vendors
TO-61 Package Details

Design hint;
Use short wires for attachment
Use large gauge wires.
Bolt the 2N6691 into a large metal plate.

PC motherboard

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Modified 6/13/15
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