2N3846 Temperature-Power Derating Curve [2N3847]
NPN Power Switching Silicon Transistor. Package, TO-63 Metal Can [TO-254AA, TO-257AA]
2N3846 Applications;
2N3846 Transistor Operational Power Derating Curve
Use the Curves to determine maximum operational power based on operational ambient temperature, derate 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 TO-63 is a Case Mount package. Check the characteristics of the heat sink to determine performance. 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.
Temperature derating is a standard design practice for electrical engineers.
Refer to MIL-PRF-19500/412D Semiconductor Device, Transistor, NPN, Silicon, Power, Types: 2N3846, 2N3846T1, 2N3846T3, 2N3847, 2N3847T1, and 2N3847T3, JAN, JANTX, JANTXV, and JANS, [TO-63]
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 Manufacturers Vendors, Transistor Derating Curves
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; MIL-PRF-19500; Semiconductor Devices, General Specification
