40 V, 200 mA PNP — the standard complement to the 2N3904
The Infineon MMBT3906LT1HTSA1 is a PNP general-purpose switching transistor in the industry-standard SOT-23-3 footprint. It is the PNP complement to the ubiquitous NPN 2N3904 / MMBT3904, rated for 40 V collector-emitter breakdown and 200 mA continuous collector current, with a transition frequency of 250 MHz.
That means Infineon has scheduled the final production window — once that window closes, the part will not be manufactured again. If you have an active BOM line using this order code, you need to secure last-time-buy inventory or qualify a drop-in replacement before the cutoff.
SOT-23-3 — what swaps in the field
The package is TO-236-3 / SC-59 / SOT-23-3, with the supplier device package marked as PG-SOT23. It is a surface-mount part, so no lab bench needed for replacement if you have a fine-tipped iron and steady hands. The 330 mW power dissipation limit means it handles small-signal duty only — do not try to pull continuous load current near 200 mA without checking the thermal derating for your ambient.