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STMicroelectronics BUL138 — Logic ICs

BUL138 NPN Transistor, 400 V 5 A TO-220, Active

MPNBUL138
End of Life

STMicroelectronics BUL138 NPN bipolar power transistor, 400 V V(BR)CEO, 5 A Ic, 80 W Pd, TO-220-3 through-hole package, ROHS3 compliant.

$1.59Ref. price · indicative, final on quote
STMicroelectronics BUL138 datasheet (PDF)
PackagingTO-220-3
RoHSROHS3 Compliant
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Aug 2026

Specifications

BUL138 specifications
ParameterValue
MountingThrough Hole
FET typeNPN
Voltage - collector emitter breakdown400 V
Current - collector (Ic)5 A
Current - collector cutoff250µA
DC current gain (hFE) (Min) @ ic, vce8 @ 2A, 5V
Power - max80 W
Operating temperature150°C (TJ)
PackageTube
CaseTO-220-3
Vce saturation (Max) @ ib, ic700mV @ 1A, 5A

Product details

400 V / 5 A NPN power transistor in TO-220

The BUL138 is an NPN bipolar power transistor rated for 400 V collector-emitter breakdown and 5 A continuous collector current, housed in a TO-220-3 through-hole package. With 80 W maximum power dissipation, it is suited for line-voltage switching applications such as flyback converters, offline power supplies, and motor-drive snubber circuits where the TO-220 package can be bolted to a heatsink.

Saturation voltage and base drive

Vce(sat) is specified at 700 mV maximum with 1 A base current driving 5 A collector current. That means the base drive circuit must supply roughly 625 mA to saturate the device at 5 A, which needs a driver stage capable of that current.

Frequently asked questions

What is the BUL138 used for?

The BUL138 is a 400 V, 5 A NPN power transistor for switching applications in offline power supplies, flyback converters, and motor drive circuits. Its TO-220 package allows mounting to a heatsink for thermal management.

Can BUL138 be used as a switch?

Yes, with a Vce(sat) of 700 mV at 5 A and a minimum hFE of 8 at 2 A, it is designed for saturated switching. The base drive must be sized to supply sufficient current for full saturation.