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NXP recently introduced a new family of BJTs with switching capabilities of up too 100V, 10A , see "The toughest bipolar transistor - 100 V in LFPAK/Power-SO8". I cannot think of a switching application where these (or any other similar) BJTs would be preferable compared to a MOSFET. Also I am very sure that there is a commercial objective behind these devices and thus there must be at least one worthwile application.

So, in what kind of application would these BJTs actually have benefits over a MOSFET?

(NB: I am referring to switching applications, not linear applications like voltage regulators.)

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  • \$\begingroup\$ Looked at the datasheet for the first one. Vce at Ic=6A is 380 mV. 0.38V/6A = 63 mOhms equivalent mosfet resistance. This is with the base current at 300 mA. Depending on the cost, this could be competitive with some mosfets. I also note that they are allowing the junction to go up to 175. I believe that is quite a bit hotter than most MOS. So these could survive with less heat sinking. \$\endgroup\$
    – user57037
    Mar 18, 2015 at 6:59
  • \$\begingroup\$ The first one is a 40V type. The worst 40V MOSFET from NXP in the same package is below 10mΩ, and to find a MOSFET that is worse than the 40V BJT you need to look in the 100V class. Temperature dependence is a good point as in a BJT the effective Ron decreases with increasing temperature, whereas in a MOSFET in increases. But is this point strong enough to justify a new product development? I think not. \$\endgroup\$
    – realtime
    Mar 18, 2015 at 8:07

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There are many applications, such as industrial controls, in which the gate of a MOSFET is just too delicate for long-term reliability. A high-voltage, yet low-energy spike that can destroy a MOSFET will simply be absorbed by a BJT and it will keep on working. Yes, you can add all sorts of external protection for the MOSFET, which may or may not work, but that just raises the BOM cost anyway.

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  • \$\begingroup\$ This approach sheds some light. The parts are qualified for automotive and that is an unfriendly environment as well. \$\endgroup\$
    – realtime
    Mar 18, 2015 at 18:45

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