onsemi BC81825MTF

Overview

BC81825MTF from Fairchild Semiconductor is an NPN epitaxial silicon transistor in SOT-23 package, rated for 25 V V_CEO, 800 mA I_C, and 310 mW power dissipation, with h_FE of 160–400 at I_C = 100 mA, used in low-power switching and AF-driver stages.

For engineers reviewing the BC81825MTF datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO rating, h_FE classification (25), saturation voltage at 500 mA, thermal resistance (403 °C/W), and SOT-23 footprint compatibility in space-constrained PCB designs.

Technical Context

The BC81825MTF operates as a general-purpose NPN bipolar junction transistor optimized for linear amplification and saturated switching. Its 25 V collector-emitter breakdown voltage and 30 V collector-base rating define its use in low-voltage DC circuits up to 24 V rail systems.

It delivers h_FE = 160–400 at V_CE = 1 V and I_C = 100 mA, with V_CE(sat) ≤ 0.7 V at I_C = 500 mA / I_B = 50 mA, and f_T = 100 MHz under 5 V / 10 mA bias - confirming suitability for audio-frequency amplification and medium-speed digital switching.

Key Specifications

Pinout & Package

SOT-23 (TO-236AB) 3-lead plastic surface-mount package with gull-wing leads; standardized land pattern per JEDEC MO-178AB; marking "8GB" identifies BC81825MTF.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC81825MTF, BC818-25-7-F offers identical electrical performance and mechanical fit, while MMBT3904LT1G trades higher voltage headroom and lower gain tolerance for broader availability and lower unit cost in sub-100 mA applications.

Availability

BC81825MTF is available at Aetrix Electronics and suitable for audio driver stages, low-voltage switching circuits, and signal inversion applications requiring stable component supply and long-term manufacturability.

Supply support for BC81825MTF 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete ICs before its acquisition by ON Semiconductor in 2016; legacy products maintain full specification compliance and support.

The BC81825MTF belongs to Fairchild's BC817/BC818 family of general-purpose NPN transistors designed for cost-effective, high-reliability switching and amplification in consumer, industrial, and automotive auxiliary circuits.

FAQ

What is the maximum collector-emitter voltage rating for BC81825MTF?

The BC81825MTF has a guaranteed V_CEO rating of 25 V, meaning it can safely sustain up to 25 V between collector and emitter with base open. This rating is verified per Fairchild's absolute maximum ratings table and defines its safe operating area in low-voltage DC applications such as 12 V or 24 V control circuits. Exceeding this voltage risks avalanche breakdown and permanent device failure. The BC81825MTF is not rated for 45 V like the BC817 variant.

Does BC81825MTF have a specified h_FE range, and how is it binned?

Yes, BC81825MTF is h_FE-binned to 160–400 at V_CE = 1 V and I_C = 100 mA, as confirmed in the "hFE Classification" table of the official datasheet. The "25" suffix explicitly denotes this gain range, enabling predictable base resistor calculation and consistent circuit behavior across production lots. This binning is measured under pulsed conditions (≤300 μs, ≤2% duty cycle) to avoid self-heating effects.

What is the saturation voltage of BC81825MTF under typical switching conditions?

The BC81825MTF exhibits V_CE(sat) ≤ 0.7 V when operated at I_C = 500 mA and I_B = 50 mA, per the Electrical Characteristics table. This low saturation voltage minimizes power dissipation (P = I_C × V_CE(sat)) during on-state operation, making the BC81825MTF suitable for efficient low-side switching of moderate-current loads such as LEDs or small relays without forced cooling.

Is BC81825MTF pin-compatible with other SOT-23 NPN transistors like MMBT3904?

Yes, BC81825MTF uses the standard SOT-23 package with pin 1 = Base, pin 2 = Emitter, pin 3 = Collector - matching the JEDEC TO-236AB outline and MMBT3904 pinout. However, electrical differences exist: BC81825MTF has lower V_CEO (25 V vs. 40 V) and higher h_FE range (160–400 vs. 100–300), so direct substitution requires verification of voltage and gain requirements in the target circuit. The BC81825MTF is not a drop-in replacement without design review.

What thermal derating applies to BC81825MTF above 25°C ambient?

BC81825MTF has a thermal derating factor of 2.48 mW/°C above 25°C ambient, derived from its 310 mW maximum power dissipation and 403 °C/W junction-to-ambient thermal resistance. For example, at 75°C ambient, allowable power drops to 310 mW − (50 × 2.48) = 186 mW. This linear derating must be applied in thermally constrained layouts or high-temperature environments to prevent junction overheating beyond 150°C.