onsemi BC81840MTF

Overview

BC81840MTF from ON Semiconductor is an NPN epitaxial silicon transistor in SOT-23 package, rated for 25 V V_CEO, 800 mA I_C, and h_FE of 250–630 at I_C = 100 mA, used in low-power switching and amplifier stages for consumer audio and power management circuits.

For engineers reviewing the BC81840MTF datasheet, pinout, applications, or equivalent options, key selection criteria include verified h_FE classification (40), V_CEO derating margin, thermal resistance (403 °C/W), and SOT-23 footprint compatibility with legacy BC817/BC818 designs.

Technical Context

This device operates as a general-purpose bipolar junction transistor optimized for linear amplification and saturated switching. Its h_FE binning (250–630) ensures predictable current gain across production lots, while its 25 V collector-emitter breakdown supports 3.3 V and 5 V logic-level drive applications.

Thermal performance is defined by R_θJA = 403 °C/W on standard FR-4 PCBs, and saturation behavior is characterized at I_C = 500 mA / I_B = 50 mA with V_CE(sat) ≤ 0.7 V - enabling efficient low-side switching in portable DC-DC feedback paths and LED drivers.

Key Specifications

Pinout & Package

SOT-23 (TO-236AB) 3-lead plastic surface-mount package with gull-wing leads; JEDEC-compliant land pattern (2.40 mm × 1.30 mm body, 0.95 mm height); marked "8GC" on top surface.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC81840MTF, BC818-40,115 offers better thermal performance and extended voltage capability, while MMBT4401LT1G trades gain stability for higher breakdown - making BC81840MTF optimal for precision low-voltage amplification and tightly regulated switching.

Availability

BC81840MTF is available at Aetrix Electronics and suitable for audio pre-amplifiers, microcontroller GPIO drivers, and DC-DC feedback circuits requiring stable component supply, consistent h_FE binning, and SOT-23 footprint reliability.

Supply support for BC81840MTF 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

ON Semiconductor is a global semiconductor supplier delivering energy-efficient power and signal management solutions for automotive, industrial, cloud computing, and consumer electronics.

The BC81840MTF belongs to ON Semiconductor's general-purpose bipolar transistor product line, designed specifically for cost-sensitive, high-volume applications requiring reliable gain matching, low saturation voltage, and JEDEC-standard packaging.

FAQ

What is the h_FE range guaranteed for BC81840MTF?

The BC81840MTF is binned to h_FE = 250–630 at V_CE = 1 V and I_C = 100 mA, as confirmed in the Fairchild/ON Semiconductor datasheet Rev. 1.1.0. This classification ensures predictable current gain for biasing and amplification tasks. The BC81840MTF's h_FE remains stable across its operating temperature range, supporting repeatable circuit behavior in production designs.

Is BC81840MTF pin-compatible with BC817 variants?

Yes, BC81840MTF shares identical SOT-23 pinout (Base–Emitter–Collector) and mechanical footprint with BC817 variants, including BC81716MTF and BC81740MTF. However, BC81840MTF has lower V_CEO (25 V vs. 45 V) and different h_FE bins - direct substitution requires verification of voltage stress and gain requirements in the target circuit. The BC81840MTF is not a drop-in replacement where 45 V breakdown is essential.

What is the maximum power dissipation of BC81840MTF at 70°C ambient?

At T_A = 70 °C, BC81840MTF's maximum power dissipation is 196 mW, calculated as P_D = 310 mW − (70 − 25) × 2.48 mW/°C. This value assumes standard FR-4 PCB mounting per JEDEC test conditions. Derating must be applied in enclosed or high-convection environments. The BC81840MTF's thermal resistance (R_θJA = 403 °C/W) directly determines this limit.

Does BC81840MTF support switching at 100 kHz?

Yes, BC81840MTF supports switching at 100 kHz in low-duty-cycle applications due to its f_T = 100 MHz and fast turn-on/turn-off characteristics (typical t_on/t_off < 100 ns). However, full-swing switching at 100 kHz requires careful attention to base drive strength and load capacitance. The BC81840MTF is commonly used in such roles within DC-DC converter feedback paths and LED dimming circuits.

What marking code identifies BC81840MTF on the package?

The BC81840MTF is marked "8GC" on the top surface of its SOT-23 package, per the ordering information table in the BC817/BC818 datasheet Rev. 1.1.0. This 3-character code distinguishes it from other h_FE bins (e.g., "8GA" for BC81816MTF) and confirms the BC81840MTF's specific gain classification and device family.