Diodes Incorporated MMBT3904T-7

Overview

MMBT3904T-7 from Diodes Incorporated is an NPN small-signal surface-mount transistor in SOT-523 package, rated for 40 V V_CEO, 200 mA I_C, and 150 mW P_D, with h_FE = 100–300 at I_C = 10 mA, used in general-purpose switching and amplification circuits on space-constrained PCBs.

For engineers reviewing the MMBT3904T-7 datasheet, MMBT3904T-7 pinout, MMBT3904T-7 application, or MMBT3904T-7 equivalent, key selection factors include its ultra-small SOT-523 footprint, guaranteed h_FE range across operating current, low V_CE(SAT) of 0.20 V at 10 mA/1 mA drive, and RoHS-compliant matte tin plating.

Technical Context

This epitaxial planar NPN transistor operates as a discrete active switch or linear amplifier in low-power analog and digital signal paths. Its design supports DC biasing and pulse switching up to 300 MHz f_T, with thermal resistance R_JA = 833 °C/W on standard FR-4 layout per AP02001.

It features complementary pairing with MMBT3906T (PNP), shares identical SOT-523 mechanical dimensions, and maintains stable gain (h_FE) across –55°C to +150°C junction temperature range under specified test conditions.

Key Specifications

Pinout & Package

SOT-523 is a 3-pin ultra-small surface-mount plastic package (1.60 mm × 0.80 mm × 0.50 mm), UL 94V-0 rated, with moisture sensitivity level 1 and matte tin lead finish compatible with lead-free reflow.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN small-signal transistor applications.

Compared with BC847BW and PN2222A, the MMBT3904T-7 delivers optimal trade-off between miniaturization, gain stability, and switching speed-making it preferred for space-constrained, battery-powered systems requiring predictable low-current gain behavior.

Availability

MMBT3904T-7 is available at Aetrix Electronics and suitable for automotive cabin sensors, USB-C port protection, and medical pulse oximeter front-end designs requiring stable component supply and tight manufacturing tolerances.

Supply support for MMBT3904T-7 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, cost-optimized components for industrial, computing, and consumer markets.

The MMBT3904T-7 belongs to Diodes' small-signal transistor product line, engineered for high-volume, space-sensitive applications where consistent gain, low saturation voltage, and RoHS compliance are mandatory.

FAQ

Is MMBT3904T-7 pin-compatible with standard SOT-23 NPN transistors?

No. The MMBT3904T-7 uses the SOT-523 package, which has different pin spacing (0.90–1.10 mm pitch) and smaller body dimensions than SOT-23 (2.3 mm × 1.3 mm). Direct replacement requires PCB layout revision and pad redesign per AP02001 guidelines.

What is the maximum operating temperature for continuous use?

The MMBT3904T-7 supports continuous operation from –55°C to +150°C junction temperature. At ambient temperatures above 25°C, power dissipation must be derated linearly per the curve in Figure 1 (833 °C/W R_JA), reaching zero at ~145°C ambient on standard FR-4.

Does this part support lead-free reflow soldering?

Yes. The MMBT3904T-7 is qualified for lead-free reflow per J-STD-020C Level 1, with matte tin plating over Alloy 42 leadframe. Peak reflow temperature up to 260°C is supported without degradation of electrical parameters or mechanical integrity.

How does h_FE vary with collector current?

Per Figure 3, h_FE peaks near 100–300 at I_C = 10 mA, drops to ~60 at I_C = 100 mA, and falls below 40 at I_C = 100 µA. Designers should select bias points within the 1–50 mA range for optimal linearity and gain stability across temperature.