The maximum drain current $I_{DM}$ is set so that latchup is avoided and so problems with connecting wires from the chip to the case or in thin f‌ilm metallizations are avoided. There is also a maximum permissible gate-source voltage $V_{GS(max)}$. The value of this voltage is set by gate oxide breakdown considerations. The IGBT is designed so that when this gate-source voltage is applied, the maximum current that can f‌low under fault (short- circuit) conditions is approximately 4 to 10 times the nominal rated current. Under these conditions the IGBT will be in the active region with a drain-source voltage equal to the off-state voltage. Recent measurements indicate that the device can withstand such currents for 5-10 microseconds depending on the value of $V_{DS}$ and can be turned off by $V_{GS}$.

The maximum drain-source voltage is set by the breakdown voltage of the pnp transistor. The beta of the transistor is quite small, so its breakdown voltage is essentially $BV_{CBO}$, the breakdown voltage of the drift-body junction (junction .$J_2$ in Fig 1). Devices with blocking capabilities as large as 1700 V are commercially available and devices with larger voltage ratings are in development.

The maximum permissible junction temperature in commercially available IGBTs is $150^°C$. The IGBT can be designed to have an on-state voltage that changes little between room temperature and the maximum junction temperature. The reason for this is the combination of positive temperature coeff‌icient of the MOSFET section and the negative temperature coeff‌icient of the voltage drop across the drift region.

Individual lGBTs are available that have nominal current ratings as large as 200-400 amperes. IGBTs are easily paralleled because of the good control over the variation of IGBT parameters from one device to another and also because of the small variation in on-state voltage with temperature. As many as four to six IGBTs connected in parallel are available as modules which have current ratings of 1000 to 1500 amperes.

The IGBT has robust SOAs both during turn-on and turn-off. The forward-bias safe operating area shown in Fig. 2 is square for short switching times, identical to the FBSOA of the power MOSFET for turn-on times shorter than 1 ms. For longer switching times the IGBT is thermally limited. as shown in the FBSOA. and this is also identical to the behavior FBSOA of the power MOSFET.

The reverse-bias safe operating area RBSOA is somewhat different than the FBSOA. as is illustrated in Fig. 2. The upper-right-hand corner of the RBSOA is progressively cut out and the RBSOA becomes smaller as the rate of change of reapplied drain-to-source voltage $dv_{DS}/dt$ becomes larger. The reason for this restriction on the RBSOA as a function of reapplied $dv_{DS}/dt$ is to avoid latchup. Too large a value of $dv_{DS}/dt$ during turn-off will cause latchup of the IGBT exactly as it can in thyristors and GTO. Fortunately, this value is quite large, comparing favorably with other power devices. In addition, the device user can easily control the reapplied $dv_{DS}/dt$ by proper choice of $V_{GG}$ and gate drive resistance.