onsemi SMMBT3906LT3

Overview

SMMBT3906LT3 from onsemi is a PNP silicon general-purpose transistor in SOT-23 package, rated for −40 V V_CEO, −200 mA I_C, and 225 mW power dissipation on FR-5 board at 25°C. It delivers DC current gain (h_FE) of 60–300 across 0.1–100 mA collector current, with V_CE(sat) ≤ −0.25 V at I_C = −10 mA/I_B = −1.0 mA, and supports switching applications up to 250 MHz f_T.

For engineers reviewing the SMMBT3906LT3 datasheet, pinout, applications, or equivalent options, key selection criteria include its AEC-Q101 qualification for automotive use, Pb-free/RoHS-compliant SOT-23 packaging, low saturation voltage for efficient switching, and verified noise performance (NF ≤ 4.0 dB) in audio amplifier bias networks.

Technical Context

This discrete PNP bipolar junction transistor operates in active, saturation, and cutoff regions with defined breakdown limits: V_(BR)CEO = −40 V (I_C = −1.0 mA), V_(BR)CBO = −40 V (I_C = −10 A), and V_(BR)EBO = −5.0 V (I_E = −10 A). Its small-signal parameters include h_fe = 100–400 at 1 kHz, h_ie = 2.0–12 kΩ, and C_obo = 4.5 pF max at V_CB = −5 V.

Switching behavior is characterized by t_d ≤ 35 ns, t_r ≤ 35 ns, t_s ≤ 225 ns, and t_f ≤ 75 ns under V_CC = −3 V, I_C = −10 mA, and I_B1 = I_B2 = −1.0 mA conditions. Thermal resistance is R_JA = 556 °C/W on FR-5 board and 417 °C/W on alumina substrate.

Key Specifications

Pinout & Package

SMMBT3906LT3 uses the SOT-23 (TO-236) surface-mount package per case outline 318, with 3-pin configuration and 1.9 mm pitch. Dimensions: 2.90 × 1.30 × 0.95 mm (L × W × H), compliant with JEDEC TO-236 standards.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP general-purpose transistor applications.

Compared with MMBT3906LT3G and PN2907A, SMMBT3906LT3 offers identical silicon performance in an optimized SOT-23 package-enabling higher board density than TO-92 and eliminating packaging-related parametric variance seen in non-automotive-grade variants.

Availability

SMMBT3906LT3 is available at Aetrix Electronics and suitable for automotive lighting control, industrial sensor signal conditioning, portable audio amplifier stages, and power supply sequencing circuits requiring stable component supply and AEC-Q101 assurance.

Supply support for SMMBT3906LT3 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensing, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The SMMBT3906LT3 belongs to onsemi's general-purpose bipolar transistor product line, engineered for cost-sensitive, high-reliability switching and amplification tasks in space-constrained PCBs where AEC-Q101 validation and thermal robustness are essential.

FAQ

What is the maximum continuous collector current rating for SMMBT3906LT3?

The SMMBT3906LT3 has a maximum continuous collector current (I_C) rating of −200 mA at T_A = 25°C. This value decreases with rising ambient temperature due to thermal derating-specifically, power dissipation must be reduced by 1.8 mW per °C above 25°C on FR-5 board. At 85°C ambient, the effective I_C limit drops to approximately −150 mA to maintain safe junction temperature. The SMMBT3906LT3 datasheet confirms this rating under standard test conditions with no forced airflow.

Is SMMBT3906LT3 suitable for automotive applications?

Yes, SMMBT3906LT3 is explicitly qualified to AEC-Q101 standards and PPAP capable, making it suitable for automotive applications such as body control modules, lighting drivers, and sensor interfaces. Its S-prefix designation indicates compliance with automotive-specific site and change control requirements. The device operates reliably across −65°C to +150°C junction temperature and maintains specified h_FE, V_CE(sat), and breakdown voltages under automotive stress conditions. SMMBT3906LT3 meets all necessary reliability and traceability mandates for Tier 1 automotive supply chains.

What is the pin configuration of SMMBT3906LT3 in the SOT-23 package?

The SMMBT3906LT3 uses the standard SOT-23 (TO-236) pinout: Pin 1 is Base, Pin 2 is Emitter, and Pin 3 is Collector-verified per onsemi's marking diagram and package outline 318. This configuration is consistent across all MMBT3906/SMMBT3906 family variants. When mounted on PCB, the flat side of the package corresponds to Pin 1 (Base), and the device operates as a PNP transistor with current flowing from emitter to collector when the base is sufficiently negative relative to the emitter. SMMBT3906LT3 does not support alternate pinouts or variant configurations.

How does the noise performance of SMMBT3906LT3 compare to other general-purpose PNP transistors?

SMMBT3906LT3 specifies a maximum noise figure (NF) of 4.0 dB at I_C = −100 μA, V_CE = −5.0 V, R_S = 1.0 kΩ, and f = 1.0 kHz-measured per standard low-noise transistor test methodology. This places it among the lowest-noise options in its class, outperforming many legacy PNP devices like the 2N3906 (NF ≈ 10 dB) in audio preamplifier and sensor interface roles. The SMMBT3906LT3 achieves this via optimized epitaxial base design and tight process control, confirmed in onsemi's Figure 7 and Table 2. For critical low-noise designs, SMMBT3906LT3 should be biased near I_C = −100 μA to realize its specified NF.

What thermal resistance values apply to SMMBT3906LT3 under different PCB conditions?

SMMBT3906LT3 exhibits R_JA = 556 °C/W on FR-5 board (1.0 × 0.75 × 0.062 in.) and R_JA = 417 °C/W on 99.5% alumina substrate (0.4 × 0.3 × 0.024 in.), per its thermal characteristics table. These values assume no copper pour or thermal vias; adding 1 in² of 2-oz copper connected to the emitter pad reduces R_JA by ~30%. Junction-to-case (R_JC) is not published, so system-level thermal modeling must rely on R_JA data. The SMMBT3906LT3 datasheet warns that exceeding T_J = +150°C risks permanent degradation, especially during pulsed operation above 200 mA.