50V dual NPN/PNP in a SOT-753 — a compact complementary pair
The ROHM FMY1AT148 packs an NPN and a PNP transistor in a single SOT-753 (SC-74A) package, emitter-coupled for a compact push-pull or complementary output stage. Each side is rated for 50V collector-emitter breakdown and 150mA continuous collector current, placing this firmly in the small-signal class — think level shifters, pre-driver buffers, audio line drivers, and general-purpose logic translation on 12V or 24V rails where you need both polarities without taking up two separate transistor footprints.
180/140 MHz fT — fast enough for moderate-speed switching and audio
The transition frequency is 180MHz for the NPN side and 140MHz for the PNP side. That puts it well above audio-band requirements and into the range of moderate-speed switching — good for gate-drive buffers in low-frequency converters, relay coil drivers, or as a pre-driver for a larger complementary pair. Not a part for RF front-ends or high-speed digital line drivers, but for the typical 100 kHz to a few MHz switching it has plenty of gain-bandwidth margin.
Saturation voltage and gain — what the 400/500 mV and hFE tell you
Vce(sat) is specified at 400 mV max for the NPN (at 5 mA base, 50 mA collector) and 500 mV max for the PNP under the same drive conditions. That's typical for a small-signal transistor — the saturation voltage won't limit you at signal-level currents, but if you're driving the full 150 mA near the maximum rating, the 500 mV drop plus the 300 mW total package dissipation limit will be the binding constraint. DC current gain (hFE) is a minimum of 120 at 1 mA, 6V, which gives consistent beta across the active region for analog bias design.