Diodes Incorporated MMST3904-7-F

Overview

MMST3904-7-F from Diodes Incorporated is a 40V, 200mA NPN small-signal transistor in SOT323 package, featuring BV_CEO ≥ 40V, h_FE = 40–300 (IC = 100µA–100mA), V_CE(SAT) ≤ 0.30V (IC = 50mA, IB = 5mA), and AEC-Q101 qualification for automotive-grade reliability. It serves as a general-purpose switching and amplification device in compact DC-DC bias networks, LED drivers, and sensor interface stages.

For engineers reviewing the MMST3904-7-F datasheet, MMST3904-7-F pinout, MMST3904-7-F application, or MMST3904-7-F equivalent, key selection criteria include its SOT323 footprint compatibility, 200mW power dissipation limit at +25°C, 625°C/W θ_JA, ESD HBM rating of 4kV, and complementary pairing with MMST3906 in dual-transistor designs.

Technical Context

This NPN bipolar junction transistor uses epitaxial planar die construction for stable gain and low leakage. Its 40V V_CEO and 60V V_CBO support medium-voltage logic-level switching, while f_T = 300MHz enables RF preamp and high-speed digital switching up to ~10MHz.

Thermal derating begins above +25°C ambient, with full 200mW dissipation only at T_A ≤ +25°C and linear reduction to zero at +150°C. The SOT323 package provides minimal thermal resistance (θ_JA = 625°C/W) on standard 1oz FR-4 PCBs under still-air conditions.

Key Specifications

Pinout & Package

SOT323 is a 3-pin ultra-small surface-mount plastic package (2.15 × 2.10 × 0.95 mm), with matte tin-plated leads solderable per MIL-STD-202 Method 208 and moisture sensitivity level 1 per J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC847BW and MMBT3904LT1G, MMST3904-7-F uniquely combines AEC-Q101 compliance, SOT323 miniaturization, and 4kV ESD HBM in one package-making it optimal for next-gen automotive modules where space, reliability, and ESD robustness are co-constrained.

Availability

MMST3904-7-F is available at Aetrix Electronics and suitable for automotive lighting control, portable sensor signal conditioning, industrial PLC input isolation, and USB-C power path switching requiring stable component supply across production lifecycles.

Supply support for MMST3904-7-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, manufacturing, and sales operations across Asia, Europe, and North America.

The MMST3904 belongs to Diodes' AEC-Q101-qualified small-signal transistor product line, engineered for automotive, industrial, and portable electronics where reliability, miniaturization, and consistent parametric performance are essential.

FAQ

What is the maximum continuous collector current for MMST3904-7-F?

The absolute maximum continuous collector current is 200 mA at T_A = +25°C. Derating is required above this temperature: power dissipation drops linearly to zero at +150°C ambient, governed by R_θJA = 625°C/W. At +85°C ambient, max I_C is approximately 120 mA under typical PCB conditions.

Is MMST3904-7-F suitable for high-frequency amplifier applications?

Yes-it has a current gain–bandwidth product (f_T) of 300 MHz at V_CE = 20V and I_C = 10mA, enabling stable small-signal amplification up to VHF frequencies. However, noise figure (NF ≤ 5 dB at 1 MHz) and input/output capacitance (C_ibo ≤ 8 pF, C_obo ≤ 4 pF) make it best suited for IF stages or low-noise preamps-not RF front-ends above 100 MHz.

How does the SOT323 package affect thermal performance?

The SOT323 package delivers a junction-to-ambient thermal resistance (R_θJA) of 625°C/W on a standard 1oz copper, single-sided FR-4 PCB under still-air conditions. This means a 200 mW power dissipation raises junction temperature by 125°C above ambient. For sustained operation, ambient must stay below +25°C unless additional copper pour or airflow is applied.

Can MMST3904-7-F be used as a direct replacement for BC847B in existing designs?

No-while both are NPN transistors with similar h_FE and V_CEO, MMST3904-7-F uses SOT323 (2.15 × 2.10 mm), whereas BC847B is typically in SOT23 (2.9 × 1.3 mm). Pinout orientation differs (SOT323: E-B-C left-to-right; SOT23: E-B-C right-to-left), and MMST3904-7-F has AEC-Q101 qualification and higher ESD rating (4 kV HBM vs. ~2 kV), requiring layout and reliability validation before substitution.