Diodes Incorporated FMMT38CQTA

Overview

FMMT38CQTA from Diodes Incorporated is an AEC-Q101-qualified NPN medium-power Darlington transistor in SOT23 package, featuring V_CEO = 60 V, I_C = 300 mA continuous, h_FE ≥ 5,000 at I_C = 100 mA, V_CE(SAT) = 0.89 V (typ.) at I_C = 800 mA / I_B = 8 mA, and 330 mW power dissipation - used for high-gain switching in automotive body control modules.

For engineers reviewing the FMMT38CQTA datasheet, FMMT38CQTA pinout, FMMT38CQTA application, or FMMT38CQTA equivalent, key selection criteria include Darlington current gain stability at 500 mA, AEC-Q101 qualification status, SOT23 thermal resistance (R_θJA = 378 °C/W), and ESD robustness (HBM = 2000 V).

Technical Context

This Darlington pair integrates two NPN transistors in cascade to deliver high DC current gain while maintaining single-package simplicity. It operates with a base-emitter turn-on voltage of 1.3–1.8 V and supports pulsed collector currents up to 800 mA under ≤2% duty cycle conditions.

The device is optimized for low-duty-cycle switching in automotive environments, where its 60 V V_CEO, 10 V V_EBO, and -55°C to +150°C operating range ensure reliability across under-hood temperature excursions and load-dump transients.

Key Specifications

Pinout & Package

Package: SOT23 - surface-mount plastic package with matte tin-plated leads, UL 94V-0 flammability rating, and moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX1051A and BC817-40,215, FMMT38CQTA uniquely delivers automotive-grade reliability, Darlington-level gain in SOT23, and validated thermal performance for pulse-loaded automotive loads - making it irreplaceable where AEC-Q101 compliance and high h_FE coexist in space-constrained layouts.

Availability

FMMT38CQTA is available at Aetrix Electronics and suitable for automotive body control, industrial solenoid actuation, and smart-fuse replacement circuits requiring stable component supply and long-term lifecycle assurance.

Supply support for FMMT38CQTA 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, specializing in high-reliability components for automotive, industrial, and computing markets.

FMMT38CQTA belongs to Diodes' AEC-Q101-qualified discrete transistor portfolio, engineered specifically for high-gain, medium-power switching in harsh-environment automotive subsystems.

FAQ

What is the maximum allowable pulsed collector current for FMMT38CQTA?

The absolute maximum pulsed collector current (I_CM) is 800 mA, specified under pulsed conditions with pulse width ≤ 300 µs and duty cycle ≤ 2%. This rating assumes adequate thermal management and is not sustainable under DC conditions due to power dissipation limits.

Does FMMT38CQTA require a base resistor when driven by a 3.3 V MCU GPIO?

Yes - a series base resistor is required to limit base current. For 800 mA collector current, ~8 mA base drive is needed; with V_BE(ON) ≈ 1.5 V, a 220 Ω resistor ensures proper saturation while protecting the GPIO pin from excessive current draw.

How does the SOT23 package affect thermal performance in continuous operation?

With R_θJA = 378 °C/W on standard FR4, continuous 300 mA operation at V_CE(SAT) ≈ 0.9 V yields ~270 mW dissipation, raising junction temperature by ~102°C above ambient - requiring derating above +50°C ambient or PCB copper enhancement for sustained use.

Is FMMT38CQTA suitable for inductive load switching without external protection?

No - although rated for 60 V V_CEO, flyback voltage from inductive loads (e.g., solenoids, motors) can exceed this. An external freewheeling diode must be placed across the load to clamp inductive kickback and prevent device breakdown during turn-off.