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6

SAFE OPERATING AREA

The Forward Biased Safe Operating Area curves define

the maximum simultaneous drain−to−source voltage and

drain current that a transistor can handle safely when it is

forward biased. Curves are based upon maximum peak

°C.

Peak repetitive pulsed power limits are determined by using

the thermal response data in conjunction with the procedures

discussed in AN569, “Transient Thermal Resistance −

General Data and Its Use.”

Switching between the off−state and the on−state may

traverse any load line provided neither rated peak current

ms. In addition the total

power averaged over a complete switching cycle must not

A Power MOSFET designated E−FET can be safely used

in switching circuits with unclamped inductive loads. For

reliable operation, the stored energy from circuit inductance

dissipated in the transistor while in avalanche must be less

than the rated limit and adjusted for operating conditions

differing from those specified. Although industry practice is

to rate in terms of energy, avalanche energy capability is not

a constant. The energy rating decreases non−linearly with an

increase of peak current in avalanche and peak junction

temperature.

Although many E−FETs can withstand the stress of

drain−to−source avalanche at currents up to rated pulsed

The energy rating must be derated for temperature as shown

in the accompanying graph (Figure 12). Maximum energy at

equal the values indicated.

Figure 11. Maximum Rated Forward Biased

Safe Operating Area

0.1

1

100

Figure 12. Thermal Response

1

100

THERMAL LIMIT

PACKAGE LIMIT

0.1

10

10

SINGLE PULSE

1 ms

100

ms

10 ms

dc

10

ms

t, TIME (s)

0.1

1.0

0.01

0.2

D = 0.5

0.05

0.01

SINGLE PULSE

D CURVES APPLY FOR POWER

PULSE TRAIN SHOWN

110

0.1

0.01

0.001

0.0001

0.00001

0.1