onsemi MMBT4403K

Overview

MMBT4403K from Fairchild Semiconductor is a PNP epitaxial silicon switching transistor in SOT-23 package, rated for -40 V V_CEO, -600 mA I_C, 350 mW P_C, with h_FE = 100 at I_C = -10 mA and f_T = 200 MHz. It serves as a general-purpose low-power switch in DC-DC converter bias circuits, LED drivers, and level-shifting interfaces.

For engineers reviewing the MMBT4403K datasheet, pinout, applications, or equivalent options, key selection criteria include its verified -40 V breakdown rating, SOT-23 thermal performance up to 150°C junction temperature, saturation voltage of -0.4 V at -150 mA/-15 mA drive, and documented turn-off time of 255 ns under defined test conditions.

Technical Context

This PNP bipolar junction transistor uses epitaxial base construction to achieve stable current gain and fast switching response. Its design supports linear amplification at low currents (h_FE ≥ 30 at -0.1 mA) and robust saturation at high drive levels (V_CE(sat) = -0.75 V at -500 mA/-50 mA).

The device operates across -55°C to +150°C, with Cob = 8.5 pF at -10 V V_CB, enabling use in moderate-frequency (<200 MHz) switching nodes. Turn-on/turn-off timing is characterized under pulsed conditions (≤300 µs, ≤2% duty cycle), confirming suitability for PWM-controlled loads.

Key Specifications

Pinout & Package

SOT-23 plastic surface-mount package with gull-wing leads; 1.90 mm × 1.30 mm footprint, 1.14 mm max height, and JEDEC-standard pin assignment.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBT4403 and PN2907A, the MMBT4403K delivers identical core switching performance in a standardized SOT-23 footprint with tighter parametric control, while the TO-92 PN2907A trades miniaturization and speed for mechanical serviceability and legacy compatibility.

Availability

MMBT4403K is available at Aetrix Electronics and suitable for power supply biasing, LED current switching, level translation, and signal inversion requiring stable component supply across industrial, automotive, and consumer electronics programs.

Supply support for MMBT4403K 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

Fairchild Semiconductor was a U.S.-based designer of analog and discrete semiconductors, acquired by ON Semiconductor in 2016; its legacy products remain widely deployed in industrial and automotive systems.

The MMBT4403K belongs to Fairchild's general-purpose bipolar transistor family, engineered for cost-sensitive, medium-speed switching in space-constrained PCB designs where reliability across extended temperature ranges is essential.

FAQ

What is the maximum continuous collector current rating for the MMBT4403K?

The MMBT4403K has a maximum continuous collector current (I_C) rating of -600 mA at T_A = 25°C. This value decreases with rising ambient temperature due to thermal derating-refer to Figure 6 in the Rev. C datasheet showing power dissipation vs. ambient temperature. At 100°C ambient, usable I_C drops to approximately -350 mA under natural convection conditions. The MMBT4403K must be operated within these limits to avoid junction overheating and permanent degradation.

Is the MMBT4403K pin-compatible with the MMBT4401?

No, the MMBT4403K is not pin-compatible with the MMBT4401. The MMBT4403K is a PNP transistor with pinout Base–Emitter–Collector (1–2–3), whereas the MMBT4401 is an NPN device with identical SOT-23 physical package but reversed polarity and different internal doping. Swapping them without circuit redesign will result in non-functional or damaged operation. Always verify polarity and pin function before substitution-the MMBT4403K must be used only in PNP-configured circuits.

What does the "K" suffix in MMBT4403K signify?

The "K" suffix in MMBT4403K denotes a specific manufacturing revision and marking variant defined in Fairchild's Rev. C datasheet. It indicates updated wafer processing, final test screening, or traceability enhancements relative to earlier MMBT4403 versions. Electrically and thermally, the MMBT4403K is fully equivalent to the base MMBT4403, but the K-marked version reflects compliance with Rev. C test conditions and parameter limits-including the 255 ns t_OFF measurement protocol.

Can the MMBT4403K be used in linear amplification applications?

The MMBT4403K can operate in the active region for small-signal amplification, with h_FE specified from -0.1 mA to -10 mA and f_T = 200 MHz. However, it is optimized as a switching transistor-not a precision amplifier-so parameters like linearity, noise figure, and gain flatness are not characterized. For linear applications requiring stability or low distortion, purpose-built RF or audio transistors (e.g., MMBT5551) are preferred. The MMBT4403K remains appropriate for simple gain stages where switching integrity is secondary.

What is the guaranteed minimum h_FE for the MMBT4403K at I_C = -1.0 mA?

The guaranteed minimum h_FE for the MMBT4403K at I_C = -1.0 mA and V_CE = -1 V is 60, as specified in the "Electrical Characteristics" table of the Rev. C datasheet. This value ensures predictable base current requirements (I_B ≤ -16.7 µA) for reliable saturation in low-current switching roles such as microcontroller output buffering or sensor interface enable control. The MMBT4403K maintains this gain down to -55°C, supporting cold-environment operation.