onsemi BC449A

Overview

BC449A from ON Semiconductor is an NPN silicon general-purpose high-voltage transistor rated for 100 V_CEO, 300 mA continuous collector current, and 1.5 W total device dissipation at T_C = 25°C. It delivers h_FE of 120–220 (at I_C = 10 mA, V_CE = 5 V) and f_T up to 200 MHz, supporting switching and linear amplification in power supply control, relay drivers, and industrial interface circuits.

For engineers reviewing the BC449A datasheet, pinout, applications, or equivalent options, key selection criteria include its 100 V_CEO rating, TO-92 package thermal performance (R_JC = 83.3°C/W), h_FE binning consistency across I_C = 10–100 mA, and Pb-free compliance per ON Semiconductor's MSL 1 handling standard.

Technical Context

The BC449A operates as a discrete NPN bipolar junction transistor optimized for medium-voltage, medium-current switching and analog amplification. Its design supports stable DC current gain (h_FE ≥ 120 at I_C = 10 mA) and low saturation voltage (V_CE(sat) ≤ 0.25 V at I_C = 100 mA, I_B = 10 mA), enabling efficient drive in inductive load interfaces.

Thermally, it leverages the TO-92 case (Case 29, Style 17) with validated R_JA = 200°C/W and R_JC = 83.3°C/W, allowing operation from −55°C to +150°C junction temperature. Its f_T = 100–200 MHz and C_obo/C_ibo curves confirm suitability for audio-frequency and low-MHz switching applications without RF parasitic concerns.

Key Specifications

Pinout & Package

BC449A is housed in a TO-92 plastic package (Case 29, Style 17), with standardized lead configuration and Pb-free finish (MSL 1). The package provides mechanical robustness for through-hole assembly and thermal path optimization via case-to-heatsink contact.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC449 and MPSA42, the BC449A provides the narrowest h_FE spread at mid-range collector currents, enabling simpler bias design in analog circuits while maintaining full 100 V capability-making it optimal for industrial control and regulated power supply feedback where gain predictability matters.

Availability

BC449A is available at Aetrix Electronics and suitable for industrial relay drivers, DC-DC converter feedback stages, LED constant-current modules, and audio pre-amplifier gain blocks requiring stable component supply, long-term manufacturability, and RoHS-compliant through-hole assembly.

Supply support for BC449A 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 (now part of onsemi) is a global semiconductor supplier specializing in power management, analog, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The BC449A belongs to ON Semiconductor's legacy high-voltage bipolar transistor family, designed specifically for cost-effective, reliable switching and amplification in industrial control, power conversion, and interface circuitry where 100 V standoff and TO-92 compatibility are essential.

FAQ

What is the maximum collector-emitter voltage rating for BC449A?

The BC449A has a maximum collector-emitter voltage (V_CEO) rating of 100 Vdc, verified under test condition I_C = 1.0 mAdc and I_B = 0. This rating is explicitly specified in the "OFF CHARACTERISTICS" table of the official ON Semiconductor datasheet (Rev. 3, September 2005) and applies to the BC449A variant only-not the BC447 or BC449 base variants.

Is BC449A pin-compatible with BC449 or BC447?

Yes, BC449A shares identical TO-92 package (Case 29, Style 17) and pinout-pin 1 is collector, pin 2 is base, pin 3 is emitter-as confirmed in the "MARKING DIAGRAM" and "PACKAGE DIMENSIONS" sections of the BC447/D datasheet. All three parts use the same mechanical layout and lead assignment, enabling direct physical substitution in existing PCBs.

What is the typical DC current gain (hFE) of BC449A at 10 mA collector current?

The BC449A exhibits h_FE = 120–220 (min–max) when tested at I_C = 10 mAdc and V_CE = 5.0 Vdc, per the "ELECTRICAL CHARACTERISTICS" table. This range reflects the A-grade binning that distinguishes BC449A from the standard BC449 (h_FE = 50–460 at I_C = 2 mA), confirming tighter gain control for precision applications.

Does BC449A meet RoHS requirements?

Yes, BC449A is supplied in a Pb-free TO-92 package compliant with RoHS Directive 2011/65/EU, as stated in the "Features" section ("Pb−Free Packages are Available*") and confirmed by the "G" suffix variants (e.g., BC449AG) listed in the "ORDERING INFORMATION" table. Moisture sensitivity level is rated MSL 1, indicating unlimited floor life under standard conditions.

What is the thermal resistance from junction to case (RJC) for BC449A?

The BC449A has a thermal resistance from junction to case (R_JC) of 83.3°C/W, as published in the "THERMAL CHARACTERISTICS" table of the BC447/D datasheet. This value is measured under standard test conditions (T_C = 25°C) and applies identically to BC449A due to shared TO-92 construction and die attachment methodology.