onsemi KST4401MTF

Overview

KST4401MTF from ON Semiconductor (formerly Fairchild) is an NPN epitaxial silicon switching transistor in SOT-23 package, rated for 40 V V_CEO, 600 mA I_C, and 350 mW P_C, commonly used in low-power digital switching and signal amplification circuits in consumer and industrial control modules.

For engineers reviewing the KST4401MTF datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain (h_FE = 40–300 at I_C = 0.1–500 mA), saturation voltage (V_CE(sat) = 0.4–0.75 V), switching speed (t_ON = 35 ns, t_OFF = 255 ns), and SOT-23 thermal and layout compatibility.

Technical Context

The KST4401MTF operates as a general-purpose NPN bipolar junction transistor optimized for medium-speed switching with defined breakdown limits: 60 V V_CBO, 40 V V_CEO, and 6 V V_EBO. Its h_FE varies from 20 to 300 across collector currents from 0.1 mA to 500 mA, supporting both small-signal amplification and saturated-switching roles.

It delivers f_T = 250 MHz at I_C = 20 mA and V_CE = 10 V, with Cob = 6.5 pF at V_CB = 5 V, enabling use in RF-coupled pre-driver stages and high-frequency logic interface circuits where bandwidth and capacitance are design-critical.

Key Specifications

Pinout & Package

SOT-23 plastic surface-mount package with gull-wing leads; 1.3 mm × 2.9 mm footprint, 1.1 mm height, and standard JEDEC MO-178 outline. Thermal resistance θ_JA ≈ 357°C/W (typical, on FR-4, 1-in² copper).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN switching transistor applications.

Compared with MMBT4401 and PN2222A, the KST4401MTF offers identical performance in SOT-23 with verified traceability to Fairchild's Rev. A2 specification, making it optimal for volume SMT manufacturing requiring consistent thermal profile and placement accuracy.

Availability

KST4401MTF is available at Aetrix Electronics and suitable for LED driver circuits, microcontroller GPIO expansion, relay driver stages, and small-signal amplifiers requiring stable component supply, consistent parametric yield, and long-term SMT assembly compatibility.

Supply support for KST4401MTF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

ON Semiconductor is a global semiconductor supplier delivering energy-efficient, high-performance silicon solutions for automotive, industrial, cloud computing, and IoT applications.

The KST4401MTF belongs to ON Semiconductor's general-purpose bipolar transistor product line, designed specifically for cost-sensitive, high-reliability SMT switching and amplification in consumer electronics and industrial controls.

FAQ

What is the maximum continuous collector current rating for KST4401MTF?

The KST4401MTF has a maximum continuous collector current (I_C) rating of 600 mA at T_A = 25°C. This rating assumes proper PCB thermal relief and derates linearly with increasing ambient temperature per the device's thermal resistance specification. Exceeding this current without adequate heat sinking risks thermal runaway and permanent damage to the KST4401MTF.

Is KST4401MTF pin-compatible with MMBT4401?

Yes, the KST4401MTF is pin-compatible with MMBT4401 - both use identical SOT-23 package outlines and terminal assignments (Base-Emitter-Collector on pins 1–2–3). Electrical characteristics match per Rev. A2 datasheet, and both are manufactured on the same process line. The KST4401MTF can be substituted for MMBT4401 without layout or firmware changes.

What is the typical DC current gain (h_FE) of KST4401MTF at 10 mA collector current?

At V_CE = 1 V and I_C = 10 mA, the KST4401MTF exhibits a typical DC current gain (h_FE) of 80–100, as specified in the "Electrical Characteristics" table. This value supports reliable saturation with base currents of 0.1–0.125 mA, making the KST4401MTF well-suited for low-power logic-level switching applications.

Does KST4401MTF support switching frequencies above 10 MHz?

Yes, the KST4401MTF supports switching frequencies above 10 MHz due to its f_T = 250 MHz and fast switching times (t_ON = 35 ns, t_OFF = 255 ns). In practice, clean square-wave operation up to ~5 MHz is achievable with proper base drive and load impedance; higher frequencies require attention to parasitic capacitance and layout to maintain edge fidelity in the KST4401MTF.

What is the emitter-base breakdown voltage (BVEBO) specification for KST4401MTF?

The emitter-base breakdown voltage (BVEBO) for KST4401MTF is 6 V, measured at I_E = 100 µA with collector open. This parameter defines the maximum reverse voltage allowable across the base-emitter junction before avalanche conduction begins, and must be respected in circuits where the base may be pulled below emitter potential - such as during ESD events or active pull-down configurations involving the KST4401MTF.