Designing with Field Effect Transistors
Derating curves to determine maximum drain current with different case temperatures.
General Recommendations; Transistor Derating Guidelines
Derating curves for selected Field Effect Transistors:
FET 2N6756 Derating Curve, TO-204AA Case
FET 2N6758 Derating Curve, TO-204AA Case
FET 2N6760 Derating Curve, TO-204AA Case
FET 2N6764 Derating Curve, TO-204AE Case
... FET 2N6764T1 Derating Curve, TO-254AA Case
FET 2N6766 Derating Curve, TO-204AE Case
... FET 2N6766T1 Derating Curve, TO-254AA Case
FET 2N6768 Derating Curve, TO-204AE Case
... FET 2N6768T1 Derating Curve, TO-254AA Case
FET 2N6770 Derating Curve, TO-204AE Case
... FET 2N6770T1 Derating Curve, TO-254AA Case
2N7000 Derating guidelines for an N-Channel MOSFET. TO-92, SOT-23
FET Manufacturers, Field Effect Transistors
Use the figures in the graphs to determine how much to derate each parameter.
Not all device characteristics are provided, a vendor data sheet should be consulted.
Field Effect Transistor Derating Factor:
A derating factor is a generic recommendation for best practices in circuit design.
Derate maximum power dissipated by the FET to 50% of the stated maximum.
Derate maximum current conducted by the FET to 75% of the stated value.
Derate the applied voltage to the FET at 75% of the maximum allowable voltage.
The derating factor is a recommendation or guideline, while the curves should be treated as a rule. As the curves insure that the junction temperature is not exceeded, while the derating factor insures higher reliability by keeping the FET in an operating region below that shown in the data sheet.
Temperature derating is standard design practice for electrical engineers.
How to Derate Components; Guidelines for Derating Electronic Devices
Derating equations for selected Field Effect Transistors:
Low Voltage Complementary Pairs
ZXMD63C03X; 30V Dual N AND P-Channel Enhancement Mode MOSFET, MSOP8
Linear Derating Factor 10 mW/C
ZXMC3A18DN8; Complementary 30V Enhancement Mode MOSFET, SO8
Linear derating factor 17 mW/C
DOD and MIL Specs
MIL-PRF-19500/757
Semiconductor Device, Field Effect Transistor, P-Channel,
Radiation Hardened (TOTAL DOSE AND SINGLE EVENT EFFECTS),
Logic-Level Silicon Type 2N7624U3 and 2N7625T3
Derate linearly by 0.60 mW/C (T3) for TC > +25C; by 0.45 mW/C (U3) for TC > +25C
MIL-PRF-19500/753
Semiconductor Device, Field Effect Radiation Hardened
(TOTAL DOSE AND SINGLE EVENT EFFECTS) TRANSISTOR, N-CHANNEL,
Silicon Type 2N7580T1, 2N7582T1, 2N7584T1, AND 2N7586T1,
JANTXVR, JANTXVF, JANSR, AND JANSF [TO-254AA]
Derate linearly by 1.67 W/C for TC > +25C.
MIL-PRF-19500/751
Semiconductor Device, Field Effect Transistor, P-Channel, Silicon Type 2N7508U3,
JANTX, JANTXV, AND JANS [TO-276AA]
Derate linearly 0.6 W/C for TC > +25C
MIL-PRF-19500/750
Semiconductor Device, Field Effect Transistor, N-Channel, Silicon Type 2N7507U3,
JANTX, JANTXV, AND JANS [TO-276AA]
Derate linearly by 0.6 W/C for TC > +25C.
MIL-PRF-19500/749A
Semiconductor Device, Field Effect Transistor, P-Channel
Radiation Hardened (TOTAL DOSE AND SINGLE EVENT EFFECTS),
Silicon Types 2N7506U8 AND 2N7506U8C, [SMD]
Derate linearly by 0.185 W/C for TC > +25C.
MIL-PRF-19500/748
P-Channel Field Effect Transistor, Type 2N7505T3, [TO-257AA (T3)]
Derate linearly by 0.6 W/C for TC > +25C
2N7438 TO-205AF metal Can, Derate linearly 0.20W/C for Tc > 25C
2N7439 TO-205AF metal Can, Derate linearly 0.20W/C for Tc > 25C
2N7558 TO-263 SMD, Derate linearly 1W/C for Tc > 25C
2N7559 TO-263 SMD, Derate linearly 1.33W/C for Tc > 25C
2N7560 TO-263 SMD, Derate linearly 1W/C for Tc > 25C
2N7563 TO-247AC Tab Mount, Derate linearly 1.20W/C for Tc > 25C
2N7564 TO-247AC Tab Mount, Derate linearly 1.60W/C for Tc > 25C
2N7565 TO-247AC Tab Mount, Derate linearly 2.56W/C for Tc > 25C
Technical Note; When a FET is operating in the saturated region the drain current changes very little for substantial changes in Vds. So the FET switch is to some extent self protecting. The FET will limit it's own drain current [and source current]. Also the drain current will decrease with increasing temperature.
