2N3846 Transistor Derating Curve

2N3846 Temperature-Power Derating Curve [2N3847]
NPN Power Switching Silicon Transistor. Package, TO-63 metal Can [TO-254AA, TO-257AA]
2N3846 Applications;

2N3846 Temperature-Power Derating Curve
2N3846 Transistor Operational DC Power Derating Curve

Use the Curves to determine maximum operational power based on operational case temperature, derate DC power as required. Otherwise derate linearly 26.6mW/0C for ambient temperatures above 250C to 175C. Derate 2W/0C for case temperatures above 1000C to 1750C.
Attaching the 2N3846 transistor to a metal heat sink will lessen the requirement to power derate the device. Note that this transistor package is designed to attach to a plate which could act as a heat sink, the stud is threaded for that reason. Which in some cases is why the TO-63 is referred to as a Stud Mount package. The leads of the 2N3846 would attach to the circuit using flexible wire. Check the characteristics of the heat sink to determine performance. The lead wires will offer no additional heat dissipation, given the probable length of the wires running between the device and the circuit. However the largest possible diameter wires should be used in any case, to reduce the effect of wire resistance. The curve and calculations work for still-air, or a non-forced air system. Adding a fan to force air over the device will also lessen the requirement to power derate the device.
Derating a component over operating temperature is a standard design practice for electrical engineers during circuit design.

Refer to MIL-PRF-19500/412 NPN Power Transistor. Types defined in the standard: 2N3846 & 2N3847 [in a TO-63 package], 2N3846T1 & 2N3847T1 [in a TO-254AA package], 2N3846T3 & 2N3847T3 [in a TO-257AA], JAN, JANTX, JANTXV, and JANS

Transistor Manufacturers & Vendors, Transistor Derating Curves

2N3846 Maximum Operational Ratings:
Collector Emitter Voltage = 200 volts dc
Collector Base Voltage = 300 volts dc
Emitter Base Voltage = 10 volts dc
Power Dissipation 250C = 4 Watts
Operating Temperature = -65 to +2000C
Storage Temperature = -65 to +2000C

Transistor Pin Out; Pin 1 Emitter, Pin 2 Base, Pin 3 Collector.
The collector (hook) is electrically connected to the case. The other two terminals shall be electrically isolated from the case.

How to Derate; Guideline for Derating Electronic Components

Refer to the General Specification on Semiconductor Devices MIL-PRF-19500.

The 2N3846 does not appear to be in full production, but the part may still be stocked. Care should be used if this component is being considered in a new design. Check on the availability of the 2N3846 before committing to use this component in a circuit.

TO-63 metal Transistor Package
TO-63 Package Outline

2N3846 Transistor Safe Operating Area
2N3846 Safe Operating Area

Related Transistors:
2N3846-T1 [TO-254 case style]
2N3846-T3 [TO-257 case style]

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Modified 1/15/12
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