onsemi NST856BF3T5G

Overview

NST856BF3T5G from onsemi is a PNP general-purpose bipolar junction transistor in SOT-1123 package, rated for −65 V V_CEO, −100 mA I_C, and 290 mW power dissipation at 25°C with 432°C/W R_JA (100 mm² copper). It delivers h_FE of 220–475 at −10 mA I_C, V_CE(sat) ≤ −0.3 V at −10 mA/−0.5 mA drive, and f_T = 100 MHz - optimized for low-power amplifier and switching functions in space-constrained PCBs.

For engineers reviewing the NST856BF3T5G datasheet, pinout, applications, or equivalent options, key selection criteria include verified PNP polarity, SOT-1123 mechanical compatibility, guaranteed −65 V breakdown, low-saturation voltage under defined bias conditions, and thermal performance validated on 100 mm² copper traces.

Technical Context

This device operates as a discrete PNP BJT with fixed emitter-base and collector-base junction structures. Its DC current gain spans 220–475 at −10 mA I_C, and saturation behavior is characterized at two bias points: −10 mA/−0.5 mA and −100 mA/−5.0 mA, yielding V_CE(sat) ≤ −0.3 V and ≤ −0.8 V respectively.

Small-signal parameters include f_T = 100 MHz at −10 mA I_C, C_ibo = 10 pF, C_obo = 4.5 pF, and NF = 10 dB at −0.2 mA I_C, confirming suitability for audio-frequency amplification and low-noise preamplifier stages where bandwidth and capacitance impact stability.

Key Specifications

Pinout & Package

The NST856BF3T5G is housed in the SOT-1123 surface-mount package (Case 524AA), measuring 0.80 × 0.60 × 0.37 mm with 0.35 mm pitch. It features three terminals in a single-row configuration with exposed pad thermal path (R_JL = 143°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBT856LT1G and DXT856-7-F, the NST856BF3T5G offers the smallest footprint (SOT-1123) and lowest thermal resistance among onsemi's PNP portfolio at this rating, making it optimal for ultra-compact, thermally constrained applications where layout area is prioritized over legacy compatibility.

Availability

NST856BF3T5G is available at Aetrix Electronics and suitable for portable audio amplifiers, low-power voltage regulator pass elements, and LED dimming switches requiring stable component supply, RoHS-compliant sourcing, and consistent parametric performance across production lots.

Supply support for NST856BF3T5G 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 delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The NST856BF3T5G belongs to onsemi's general-purpose bipolar transistor product line, engineered specifically for space-constrained, low-power analog and switching circuits where high gain, low saturation voltage, and ultra-miniature packaging are critical design requirements.

FAQ

What is the maximum collector-emitter voltage rating for the NST856BF3T5G?

The NST856BF3T5G has a maximum collector-emitter voltage (V_CEO) rating of −65 Vdc, tested at I_C = −10 mA with open base. This rating applies under steady-state DC conditions and defines the absolute maximum reverse bias the transistor can withstand before breakdown. Exceeding this voltage may cause irreversible damage. The NST856BF3T5G must be operated within this limit in all circuit configurations including switching, amplification, and regulation applications.

Is the NST856BF3T5G compatible with lead-free reflow soldering processes?

Yes, the NST856BF3T5G is Pb-free and qualified for standard lead-free reflow soldering per JEDEC J-STD-020. Its SOT-1123 package uses matte tin plating and passes thermal cycling and intermetallic growth validation up to 260°C peak profile. The "G" suffix explicitly denotes compliance. The NST856BF3T5G supports both no-clean and water-wash flux chemistries and maintains parameter stability post-reflow when processed within recommended time-above-liquidus (TAL) windows.

What is the typical DC current gain (h_FE) of the NST856BF3T5G at low collector current?

The NST856BF3T5G exhibits a minimum h_FE of 150 at I_C = −2.0 mA and V_CE = −5.0 V, with a typical value of 290 and maximum of 475 under the same conditions. This wide gain range reflects process variation control and supports predictable biasing in linear amplifier designs. The NST856BF3T5G's h_FE remains stable across temperature (−55°C to +150°C), as confirmed by Figure 2 in the official datasheet.

Does the NST856BF3T5G have a specified noise figure, and under what conditions?

Yes, the NST856BF3T5G has a maximum noise figure (NF) of 10 dB, measured at I_C = −0.2 mA, V_CE = −5.0 Vdc, source resistance R_S = 2.0 kΩ, frequency f = 1.0 kHz, and bandwidth BW = 200 Hz. This specification validates its suitability for low-noise preamplifier stages in sensor signal chains. The NST856BF3T5G's NF performance is consistent with its f_T and C_ibo values, and no derating is required for operation within this test condition envelope.

How does the thermal resistance of the NST856BF3T5G vary with PCB copper area?

The NST856BF3T5G's thermal resistance junction-to-ambient (R_JA) is 432°C/W with 100 mm² of 1 oz copper and improves to 360°C/W with 500 mm² copper - a 17% reduction. This dependency is documented in Note 1 and Note 2 of the Thermal Characteristics table. The NST856BF3T5G's R_JL (junction-to-lead 3) is 143°C/W, indicating significant heat transfer through the collector pad; therefore, maximizing copper area connected to Pin 3 directly enhances thermal performance more than overall board area alone.