onsemi NST857BMX2T5G

Overview

NST857BMX2T5G from onsemi is a PNP silicon general-purpose transistor in a 1.0 × 0.6 mm X2DFN3 package, rated for −45 V V_CEO, −100 mA I_C, and 640 mW power dissipation on 100 mm² copper pad; it delivers h_FE = 220–475 at I_C = −2.0 mA and V_CE = −5.0 V, with f_T = 100 MHz, used in low-power switching and signal amplification circuits.

For engineers reviewing the NST857BMX2T5G datasheet, pinout, applications, or equivalent options, this page provides verified electrical parameters, thermal derating behavior, saturation voltage performance across operating current, noise figure (4.0 dB), and validated alternative transistors for discrete analog and switching designs.

Technical Context

This device operates as a medium-speed, low-voltage PNP bipolar junction transistor optimized for surface-mount applications where compact size and stable DC gain are critical. Its 100 MHz f_T supports audio-frequency switching and linear amplification up to ~10 MHz, while its −5.0 V V_EBO rating enables safe biasing in dual-rail configurations.

The NST857BMX2T5G exhibits two distinct thermal performance modes: 166 mW on minimal 0.6 mm² Cu pad (R_JA = 722 °C/W) and 640 mW on 100 mm² Cu pad (R_JA = 185 °C/W), requiring explicit PCB layout planning. Its V_CE(sat) remains ≤ −0.65 V at I_C = −100 mA / I_B = −5.0 mA, confirming suitability for saturated-switching roles.

Key Specifications

Pinout & Package

Package: X2DFN3 (1.0 × 0.6 mm, 0.35 mm pitch), case 714AC, surface-mount, leadless, thermally enhanced with exposed drain pad (collector-connected).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBT4403LT1G and DXT3906TC-7-F, the NST857BMX2T5G delivers superior DC gain consistency and best-in-class thermal resistance per unit area, making it optimal for space-constrained, low-power, high-reliability consumer and portable electronics.

Availability

NST857BMX2T5G is available at Aetrix Electronics and suitable for LED driver circuits, low-voltage logic interfaces, audio preamplifiers, power supply enable switches, and discrete analog signal conditioning requiring stable component supply and consistent PNP switching performance.

Supply support for NST857BMX2T5G 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, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and IoT applications.

The NST857BMX2T5G belongs to onsemi's general-purpose bipolar transistor family designed for high-volume, cost-sensitive applications demanding robust performance, small footprint, and RoHS compliance in portable and space-constrained electronics.

FAQ

What is the maximum continuous collector current for NST857BMX2T5G?

The NST857BMX2T5G has a maximum continuous collector current (I_C) of −100 mA at T_A = 25°C. This rating assumes proper PCB thermal management-specifically, mounting on a 100 mm², 2 oz. copper pad. At higher ambient temperatures, derating applies at 5.41 mW/°C above 25°C. Exceeding this current risks thermal runaway or permanent degradation of the NST857BMX2T5G.

Does NST857BMX2T5G support high-frequency signal amplification?

Yes, the NST857BMX2T5G features a current-gain bandwidth product (f_T) of 100 MHz under standard test conditions (I_C = −10 mA, V_CE = −5.0 V, f = 100 MHz). This enables effective small-signal amplification up to approximately 10 MHz with usable gain, making the NST857BMX2T5G appropriate for audio preamplifiers and RF front-end biasing-not RF power amplification.

How does the thermal performance of NST857BMX2T5G vary with PCB layout?

The NST857BMX2T5G offers two defined thermal profiles: 166 mW power dissipation with R_JA = 722 °C/W on a minimal 0.6 mm² copper pad, and 640 mW with R_JA = 185 °C/W on a 100 mm² copper pad. Layout directly determines which spec applies-so the NST857BMX2T5G's junction temperature must be calculated using the actual copper area and ambient conditions to ensure reliability.

What is the guaranteed DC current gain (h_FE) range for NST857BMX2T5G?

The NST857BMX2T5G is binned as "B" grade, guaranteeing h_FE ≥ 220 at I_C = −2.0 mA and V_CE = −5.0 V, and ≥ 290 at I_C = −10 mA. At I_C = −100 mA, h_FE remains ≥ 250. These values are tested and specified per onsemi's datasheet-no interpolation or extrapolation is needed to apply the NST857BMX2T5G in gain-critical designs.

Is NST857BMX2T5G compatible with lead-free reflow processes?

Yes, the NST857BMX2T5G is Pb-free, halogen-free/BFR-free, and RoHS compliant. It is qualified for standard lead-free reflow profiles (J-STD-020), including peak temperatures up to 260°C. The X2DFN3 package's thermal mass and material composition ensure reliable solder joint formation without delamination or voiding-critical for high-yield manufacturing of the NST857BMX2T5G.