onsemi NST3906MX2T5G

Overview

NST3906MX2T5G from onsemi is a PNP silicon general-purpose transistor in a 1.0 mm × 0.6 mm X2DFN3 package, rated for −40 V V_CEO, −200 mA continuous collector current, and 250 MHz f_T, commonly used in low-power switching and signal amplification circuits on space-constrained PCBs.

For engineers reviewing the NST3906MX2T5G datasheet, pinout, applications, or equivalent options, key selection criteria include its −40 V breakdown rating, low-profile DFN thermal performance (R_JA = 203 °C/W with 100 mm² copper), and verified DC current gain range of 30–300 across −100 μA to −100 mA I_C.

Technical Context

This PNP bipolar junction transistor operates in active, saturation, and cutoff regions with defined safe operating area (SOA) limits up to −100 mA at −2 V V_CE. Its small-signal parameters-including h_fe = 100–400 at 1 mA I_C, C_obo ≤ 4.5 pF, and NF ≤ 4.0 dB-support audio preamplifier and low-noise switching roles.

Thermal design relies on two dissipation modes: 165 mW with minimal copper (0.6 mm² pad) and 590 mW with enhanced 100 mm² copper layout. Switching performance is characterized by t_d/t_r ≤ 35 ns and t_s ≤ 225 ns under forced H_FE = 10 conditions at −3 V supply.

Key Specifications

Pinout & Package

Package: X2DFN3 (1.0 mm × 0.6 mm, 0.35 mm pitch, Case 714AC), surface-mount, leadless, bottom-thermal-pad design.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBT3906LT1G and DXT3906TC-7-F, the NST3906MX2T5G delivers superior thermal performance per unit area and smallest footprint, making it optimal for miniaturized power management and portable electronics where board space and thermal headroom are constrained.

Availability

NST3906MX2T5G is available at Aetrix Electronics and suitable for LED driver circuits, level-shifting interfaces, audio preamplifiers, and power supply enable controls requiring stable component supply and consistent parametric performance across production batches.

Supply support for NST3906MX2T5G 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 focused on energy-efficient electronics, delivering power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and IoT markets.

The NST3906MX2T5G belongs to onsemi's general-purpose bipolar transistor family designed specifically for space-constrained, low-power switching and amplification in consumer, computing, and industrial edge devices.

FAQ

What is the maximum continuous collector current rating for the NST3906MX2T5G?

The NST3906MX2T5G has a maximum continuous collector current (I_C) rating of −200 mA at T_A = 25 °C with appropriate PCB copper area. This rating assumes surface mounting on FR4 with a 100 mm², 2 oz. copper pad, which enables 590 mW total power dissipation. Derating applies above 25 °C at 4.93 mW/°C.

Does the NST3906MX2T5G have a thermal pad, and how should it be handled in PCB layout?

Yes, the NST3906MX2T5G in X2DFN3 package features an exposed thermal pad on the bottom side. For optimal thermal performance, this pad must be soldered to a minimum 100 mm² copper area on the PCB using thermal vias. The datasheet specifies R_JA = 203 °C/W only when this layout condition is met; otherwise, R_JA degrades to 720 °C/W with minimal copper.

What is the guaranteed DC current gain (h_FE) range for the NST3906MX2T5G at −10 mA collector current?

At I_C = −10 mA and V_CE = −1.0 V, the NST3906MX2T5G guarantees h_FE between 100 and 300. This range is confirmed in the Electrical Characteristics table and supports predictable biasing in linear amplifier and precision switching applications without requiring gain binning.

Can the NST3906MX2T5G replace the MMBT3906 in existing SOT-23 designs without board modifications?

No, the NST3906MX2T5G cannot directly replace the MMBT3906 without PCB layout changes. It uses the X2DFN3 (1.0 mm × 0.6 mm) package versus SOT-23 (2.9 mm × 1.3 mm), with different pinout orientation and no leads. A redesign is required to accommodate the smaller footprint, thermal pad, and solder paste stencil adjustments.

What is the typical noise figure of the NST3906MX2T5G, and under what conditions is it measured?

The NST3906MX2T5G has a maximum noise figure (NF) of 4.0 dB, measured at I_C = −100 mA, V_CE = −5.0 V, R_S = 1.0 kΩ, and f = 1.0 kHz. This value is specified in the Electrical Characteristics table and confirms suitability for low-noise analog signal conditioning in microphone and sensor front-end circuits.