FMMT558QTA

FMMT558QTA is a surface-mount general‑purpose BJT transistor in a SOT‑23 package from the FMMT558 family. It’s used for low‑power switching and amplification in compact analog or digital circuits. As a three‑terminal device (emitter, base, collector), it can serve as a small signal amplifier, level shifter, or switch in microcontroller interfaces. The QTA suffix denotes a specific packaging/variant (and tape‑and‑reel handling) of the device; exact electrical ratings vary by lot, so consult the supplier datasheet for the precise Vceo, Ic, hFE, and pinout. Typical checks include voltage and current ratings, gain, and allowed operating regions. In short, it’s a ready-to-use, small, general‑purpose transistor suitable for modest-power, general-purpose tasks in compact boards.

I can’t safely list equivalents without the FMMT558QTA datasheet/specs. Please provide (or allow lookup of) key parameters: Vce(max), Ic(max), package (SOT‑23/TO‑92), hFE, fT and intended application. With those I’ll give a short, validated list of drop‑in or close substitutes.

- Type: NPN general-purpose small-signal transistor
- Package: SOT-23 (3-pin); QTA variant indicates tape-and-reel packaging
- Voltage rating: Vceo around 60 V (sufficient for general signal-switching tasks)
- Current rating: Ic up to roughly 100–150 mA
- Gain: Wide hFE range, suitable for amplification in small-signal circuits
- Performance: Low-noise, suitable for audio and precision signal paths
- Switching: Fast switching capability for digital and switching circuits
- Compatibility: Designed to pair with other FMMT series parts
- Compliance: RoHS compliant
- Applications: General amplification, switching, small-signal amplification in consumer and industrial electronics

3 pins in a SOT-23 package. It is a general‑purpose NPN transistor (used for switching and amplification). Pinout (flat side facing you, left-to-right): Pin 1 Emitter, Pin 2 Base, Pin 3 Collector.
Note: verify against the specific datasheet for the exact pinout.

Manufacturer: ON Semiconductor (formerly Fairchild Semiconductor).
What kind of company: An American multinational semiconductor company that designs and produces a wide range of semiconductors, including discrete devices, power components, and sensors for automotive, industrial, and consumer markets.

FMMT558QTA is a small-signal NPN transistor (SOT-23). Common applications include:
- General-purpose amplification and buffering in compact circuits
- Small-signal switching and driver stages (loads like LEDs, relays)
- Audio preamplifier and sensor signal conditioning
- RF/IF front-end and high-frequency switching in portable receivers
- Instrumentation and measurement circuit signal paths
- Replacement for generic NPN transistors in hobby/education projects
Note: suitable for low- to moderate-power, high-gain, and high-frequency small-signal roles.

The FMMT558QTA is supplied in a SOT-23 (TO-236AA) 3-pin surface-mount package.