onsemi BC449

Overview

BC449 from ON Semiconductor is an NPN silicon bipolar junction transistor designed for high-voltage switching and amplification in industrial control, power supply regulation, and relay driver circuits. It features a 100 V_CEO rating, 300 mA continuous collector current, 625 mW power dissipation at T_A = 25°C, and DC current gain (h_FE) of 50–460 at I_C = 2 mA.

For engineers reviewing the BC449 datasheet, pinout, applications, or equivalent options, key selection criteria include its 100 V breakdown voltage, TO-92 package compatibility, f_T of 100–200 MHz, saturation voltage under load, and thermal resistance profile for discrete BJT-level design validation.

Technical Context

The BC449 operates as a general-purpose NPN BJT with verified high-voltage capability (V_CEO = 100 V, V_CBO = 100 V), enabling use in off-line switch-mode power supply feedback stages and inductive load switching where transient voltage suppression is critical. Its h_FE range spans 50–460 depending on bias conditions, supporting both linear amplification and saturated switching modes.

Thermal performance is defined by R_JA = 200°C/W and R_JC = 83.3°C/W, indicating suitability for through-hole PCB layouts with moderate copper area. The device supports operation from −55°C to +150°C junction temperature, with MSL Level 1 handling and Pb-free packaging compliance confirmed per ON Semiconductor documentation.

Key Specifications

Pinout & Package

BC449 is housed in a standard TO-92 (Case 29, Style 17) plastic package with 3 leads, optimized for manual assembly and wave soldering. Pin identification is fixed: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC449A and MPSA42, the BC449 balances mid-range voltage capability, broad h_FE coverage, and low saturation loss-making it optimal for cost-sensitive industrial controls where 100 V margin suffices and predictable turn-on behavior is essential.

Availability

BC449 is available at Aetrix Electronics and suitable for industrial relay drivers, linear regulator pass elements, AC line-sensing circuits, and DC motor speed control stages requiring stable component supply, long-term manufacturability, and RoHS-compliant through-hole discretes.

Supply support for BC449 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 onsemi) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC449 belongs to ON Semiconductor's legacy high-voltage BJT family, engineered for robustness in industrial automation, power conversion, and signal conditioning where reliability under voltage stress and thermal cycling is critical.

FAQ

What is the maximum collector-emitter voltage rating for BC449?

The BC449 has a guaranteed minimum V_CEO rating of 100 Vdc under test conditions (I_C = 1.0 mAdc, I_B = 0). This rating is validated per ON Semiconductor's BC447/D datasheet Rev. 3 (2005) and applies specifically to the BC449 and BC449A variants-not the BC447. Exceeding this voltage risks irreversible breakdown.

Is BC449 pin-compatible with BC449A?

Yes, BC449 and BC449A share identical TO-92 packaging, pinout (Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter), and mechanical dimensions. The only functional difference is that BC449A guarantees a minimum h_FE of 120 at I_C = 2 mA, while BC449 guarantees only 50 under the same conditions-both remain electrically interchangeable in non-gain-critical designs.

What is the typical DC current gain (hFE) of BC449 at 100 mA collector current?

At I_C = 100 mAdc and V_CE = 5.0 Vdc, the BC449 exhibits h_FE in the range of 50–60 (minimum to maximum), per the "ON CHARACTERISTICS" table in the official datasheet. This lower gain band reflects reduced beta under higher current stress and must be accounted for in base drive resistor calculations.

Does BC449 support lead-free soldering processes?

Yes, BC449 is offered in Pb-free TO-92 packaging (marked with "G" suffix, e.g., BC449G) and complies with JEDEC J-STD-020 moisture sensitivity Level 1. It is qualified for standard lead-free reflow profiles with peak temperatures up to 260°C, as documented in ON Semiconductor's Soldering and Mounting Techniques Reference Manual.

What thermal resistance values apply to BC449 in free-air conditions?

The BC449 has a junction-to-ambient thermal resistance (R_JA) of 200°C/W when mounted on a standard FR-4 PCB with no added copper area. Its junction-to-case resistance (R_JC) is 83.3°C/W, confirming that heatsinking via the collector lead is viable but requires mechanical attachment to a thermal plane for >200 mW continuous dissipation.