Diodes Incorporated FMMT3904TA

Overview

FMMT3904TA from Diodes Incorporated (formerly Zetex) is an NPN silicon planar switching transistor in SOT-23 package, rated for 40 V V_CEO, 200 mA I_C, and 330 mW P_tot at T_amb = 25°C; used in low-power digital switching, level translation, and LED driver stages in portable instrumentation and power management circuits.

For engineers reviewing the FMMT3904TA datasheet, FMMT3904TA pinout, FMMT3904TA application, or FMMT3904TA equivalent, key selection criteria include verified h_FE range (50–300 at I_C = 1–100 mA), V_CE(sat) ≤ 0.3 V at I_C/I_B = 10 mA/1 mA, f_T ≥ 250 MHz, and guaranteed SOT-23 pin compatibility with JEDEC TO-236AB outline.

Technical Context

This discrete NPN transistor operates in active and saturation regions for signal switching and current amplification. Its planar construction ensures stable h_FE across temperature (−55°C to +150°C) and low leakage (I_CEX ≤ 50 nA at V_CE = 30 V).

Designed for pulsed operation with ≤2% duty cycle, it delivers consistent t_r ≤ 35 ns and t_f ≤ 50 ns at V_CC = 3 V, I_C = 10 mA, and I_B1 = 1 mA - enabling reliable use in 1–10 MHz digital logic interfaces and PWM-controlled loads.

Key Specifications

Pinout & Package

SOT-23 (TO-236AB) plastic surface-mount package with gull-wing leads; standardized 3-pin layout compatible with automated placement and reflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC846B,215 and MMBT3904LT1G, FMMT3904TA offers broader h_FE range (50–300) for flexible base drive design, balanced speed (t_r/t_f ≤ 35/50 ns), and proven reliability in industrial temperature cycling - making it ideal for mixed-signal embedded control where parameter spread must be accommodated without redesign.

Availability

FMMT3904TA is available at Aetrix Electronics and suitable for LED drivers, digital logic interfaces, sensor load switching, and small DC motor control requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for FMMT3904TA 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 semiconductor manufacturer specializing in discrete, analog, and mixed-signal solutions for power management, signal integrity, and connectivity applications.

FMMT3904TA belongs to the Zetex legacy high-speed switching transistor product line, engineered for precision digital switching, low-voltage logic interfacing, and compact power control in space-constrained portable and industrial systems.

FAQ

Is FMMT3904TA RoHS compliant and halogen-free?

Yes, FMMT3904TA meets RoHS Directive 2011/65/EU and is certified halogen-free per IEC 61249-2-21. The SOT-23 package uses matte tin lead finish and green molding compound, with full compliance documentation available through Diodes Incorporated's quality portal.

What is the maximum allowable junction temperature during continuous operation?

The absolute maximum junction temperature is +150°C. At 200 mA I_C, thermal resistance R_θJA is 379°C/W (SOT-23, 1-in² FR-4, 1 oz Cu). Derating begins at 25°C ambient: maximum power drops to zero at ~105°C case temperature under standard PCB conditions.

Can FMMT3904TA replace BC547 in existing designs?

Yes, with verification of layout clearance and thermal margin. Both are NPN general-purpose transistors, but FMMT3904TA has higher f_T (250 MHz vs. 300 MHz typ. for BC547), lower V_CE(sat), and SOT-23 footprint versus TO-92 - requiring PCB pad revision but offering improved speed and density.

Does FMMT3904TA support pulsed current beyond 200 mA?

Yes - the datasheet specifies pulsed I_C up to 500 mA (duty cycle ≤ 2%, pulse width ≤ 300 µs). This enables short-duration surge handling in motor start-up or sensor excitation, provided average power remains within 330 mW derated for ambient temperature.