Diodes Incorporated MMST6427-7-F

Overview

MMST6427-7-F from Diodes Incorporated is an NPN surface-mount Darlington transistor in SOT-323 package, rated for 40 V V_CEO, 500 mA I_C, and 200 mW P_D, with h_FE up to 200,000 at 500 mA - optimized for low-power switching and amplification in space-constrained portable electronics.

For engineers reviewing the MMST6427-7-F datasheet, MMST6427-7-F pinout, MMST6427-7-F application, or MMST6427-7-F equivalent, this device serves as a high-gain, low-saturation-voltage switching element in battery-powered sensor interfaces, LED drivers, and microcontroller-peripheral interface circuits where compact size and current gain stability across temperature are critical.

Technical Context

This Darlington pair integrates two NPN transistors monolithically using epitaxial planar die construction, delivering ultra-high DC current gain (h_FE = 10,000–200,000) while maintaining V_CE(sat) ≤ 1.5 V at I_C = 500 mA and I_B = 0.5 mA. Its low input drive requirement enables direct interfacing with 3.3 V or 5 V logic outputs.

The device operates across –55 °C to +150 °C, with thermal resistance R_θJA = 625 °C/W on a standard FR4 PCB, and exhibits typical C_obo = 8.0 pF and C_ibo = 15 pF - supporting stable operation in low-frequency switching (<1 MHz) and analog amplification up to f_T ≈ 150 MHz at I_C = 10 mA.

Key Specifications

Pinout & Package

MMST6427-7-F uses the SOT-323 (SC-70) three-terminal plastic package with lead-free matte tin plating, moisture sensitivity level 1, and UL 94V-0 flammability rating. Weight is approximately 0.006 g.

Key Features

Applications

Equivalent & Alternatives

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

Compared with NSV6427MUTBG and ZTX851, MMST6427-7-F offers the highest guaranteed h_FE in the smallest footprint, making it optimal for ultra-low-drive, space-constrained designs - whereas NSV6427MUTBG trades marginal gain improvement for tighter spec compliance, and ZTX851 sacrifices gain and size for voltage headroom and thermal capacity.

Availability

MMST6427-7-F is available at Aetrix Electronics and suitable for portable sensor interfaces, LED driver circuits, microcontroller peripheral drivers, and low-power relay interfaces requiring stable component supply across extended product lifecycles.

Supply support for MMST6427-7-F 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design and manufacturing operations across Asia and the Americas.

The MMST6427 belongs to Diodes' general-purpose bipolar transistor product line, engineered specifically for high-gain, low-voltage switching and amplification in consumer, computing, and industrial portable electronics.

FAQ

Is MMST6427-7-F pin-compatible with standard SOT-323 NPN transistors?

Yes - MMST6427-7-F uses the industry-standard SOT-323 pinout (Emitter-Base-Collector on pins 1-2-3), matching mechanical and solder pad layouts of all SOT-323-packaged NPN transistors. However, its Darlington architecture delivers significantly higher h_FE and V_CE(sat) than single-junction equivalents, so electrical behavior differs despite identical mounting.

What is the maximum safe operating current at 85°C ambient?

At T_A = 85 °C, derating applies: P_D drops linearly from 200 mW at 25 °C to zero at 150 °C. At 85 °C, max allowable P_D = 150 mW. With V_CE(sat) ≈ 1.3 V at 500 mA, max continuous I_C ≈ 115 mA to stay within thermal limits - verified via R_θJA = 625 °C/W and junction temperature calculation.

Does MMST6427-7-F require a base resistor when driven by a 3.3 V MCU GPIO?

Yes - although h_FE is high, a base resistor is required to limit I_B and prevent excessive base-emitter forward bias. For 20 mA collector load, a 100 kΩ resistor yields ~30 µA I_B, well within safe limits and providing >100× overdrive. Omitting the resistor risks damaging the base-emitter junction under sustained 3.3 V drive.

Can MMST6427-7-F be used in linear amplification mode?

Yes - its h_FE stability and low V_BE(on) variation support Class-A amplification at I_C ≤ 10 mA. However, power dissipation must be strictly managed: at V_CE = 5 V and I_C = 10 mA, P_D = 50 mW, leaving margin below 200 mW rating. Avoid operation near V_CEO or I_C max in linear mode due to thermal runaway risk in Darlington structures.