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STMicroelectronics STPSA42 — Discrete Semiconductors

STPSA42 NPN Transistor, 300 V, 500 mA, TO-92-3, Obsolete

MPNSTPSA42
Obsolete

STMicroelectronics STPSA42 NPN transistor, TO-92-3 through-hole, 300 V Vceo, 500 mA Ic, 625 mW Pd, 50 MHz fT, 150°C junction temperature.

STMicroelectronics STPSA42 datasheet (PDF)
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Jul 2026

Specifications

STPSA42 specifications
ParameterValue
MountingThrough Hole
FET typeNPN
Voltage - collector emitter breakdown300 V
Current - collector (Ic)500 mA
Current - collector cutoff100nA (ICBO)
DC current gain (hFE) (Min) @ ic, vce40 @ 30mA, 10V
Power - max625 mW
Frequency50MHz
Operating temperature150°C(TJ)
PackageBulk
CaseTO-226-3, TO-92-3 (TO-226AA)
Vce saturation (Max) @ ib, ic500mV @ 2mA, 20mA

Product details

300 V NPN in a TO-92 — where it fits

The STPSA42 is an NPN transistor with a 300 V collector-emitter breakdown (Vceo) and 500 mA continuous collector current, housed in a TO-92-3 through-hole package. The 300 V rating puts it in the high-voltage small-signal class. The 625 mW power dissipation in the TO-92 sets a thermal ceiling.

The 300 V Vceo is the headline spec — it allows the part to survive on a 170 VDC bus (rectified 120 VAC) or a 48 V telecom rail with generous headroom. The 500 mA Ic max means this is a driver or interface transistor, not a pass element; a relay coil, a small solenoid, or an optocoupler LED drive is the right load. DC current gain (hFE) is a minimum of 40 at 30 mA, 10 V — typical gain is higher, but the 40 floor matters for saturation margin in a 20 mA load.

Obsolete — sourcing the STPSA42 today

The STPSA42 is listed as Obsolete. The TO-92-3 package is through-hole, so rework and hand-replacement in legacy boards is straightforward.

Frequently asked questions

What is the replacement for STPSA42?

A parametric cross — a 300 V NPN in TO-92 with at least 500 mA Ic and similar hFE — can be sourced from other manufacturers, but the pinout (E-B-C) and Vce(sat) must be verified against the original design.