NXP Semiconductors BF423,112

Overview

BF423,112 from NXP Semiconductors (formerly Philips) is a PNP high-voltage bipolar junction transistor in TO-92 plastic package, rated for −250 V collector-base voltage (VCBO), −250 V collector-emitter voltage (VCEO), and 830 mW total power dissipation at Tamb ≤ 25 °C; used in class-B video output stages of colour television and professional monitor equipment.

For engineers reviewing the BF423,112 datasheet, BF423,112 pinout, BF423,112 application, or BF423,112 equivalent, key selection criteria include high-voltage PNP switching capability, low feedback capacitance (≤1.6 pF), transition frequency (≥60 MHz), DC current gain (hFE ≥ 50 at −25 mA), and thermal resistance (Rth(j-a) = 150 K/W).

Technical Context

The BF423,112 operates as a high-voltage PNP switching and amplification device with avalanche-rated breakdown voltages, optimized for stable performance under high-VCE stress in video output circuits. Its low Cre (≤1.6 pF) minimizes Miller effect distortion, while fT ≥ 60 MHz supports wideband signal handling up to 100 MHz test conditions.

Designed for through-hole mounting on PCBs, it features a maximum junction temperature of 150 °C and storage temperature range from −65 °C to +150 °C. The device requires external base drive control and is not internally compensated or integrated with protection circuitry.

Key Specifications

Pinout & Package

BF423,112 is housed in a TO-92 plastic single-ended leaded (through-hole) package per SOT54 outline, with 3 leads and standard SC-43A footprint. Mounting requires PCB trace thermal relief and mechanical strain relief per IEC 60134 limiting values.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BF421,112, BF423,112 trades 50 V voltage headroom for tighter process control in mid-range CRT applications; compared with BC639, it provides essential PNP polarity and −250 V rating unattainable in general-purpose NPN transistors, preserving original schematic functionality without layout or bias network changes.

Availability

BF423,112 is available at Aetrix Electronics and suitable for colour television design, professional video monitor manufacturing, and high-voltage analog signal conditioning requiring stable component supply and long-term obsolescence management.

Supply support for BF423,112 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

NXP Semiconductors is a global semiconductor company formed from the spin-off of Philips Semiconductors in 2006, specializing in high-reliability analog, logic, and RF components for industrial and consumer systems.

The BF423,112 belongs to NXP's legacy high-voltage discrete transistor product line, originally designed for CRT-based video equipment requiring rugged PNP switching with controlled capacitance and gain stability.

FAQ

What is the maximum collector-emitter voltage rating for BF423,112?

The BF423,112 has a maximum collector-emitter voltage (VCEO) rating of −250 V with the base open, as specified in the Philips 2004 datasheet. This rating applies under steady-state DC conditions and defines the absolute maximum reverse bias the device can withstand without breakdown. Exceeding this value risks permanent damage per IEC 60134 limiting values. The BF423,112 must be operated within this limit in all applications, including video output and deflection circuits.

Is BF423,112 pin-compatible with BF421,112?

Yes, BF423,112 is pin-compatible with BF421,112 - both use identical TO-92 (SOT54) packaging and share the same pin 1 (base), pin 2 (collector), pin 3 (emitter) assignment. However, BF421,112 is rated for −300 V VCBO/VCEO versus −250 V for BF423,112. Substitution is physically possible but requires verification that system voltage stress remains within BF423,112's −250 V limit.

What is the typical transition frequency (fT) of BF423,112 and how is it measured?

The BF423,112 has a minimum transition frequency (fT) of 60 MHz, measured under standardized conditions: VCE = −10 V, IC = −10 mA, and test frequency = 100 MHz. This parameter reflects the frequency at which current gain drops to unity and confirms suitability for composite video bandwidth requirements. The fT value is guaranteed across production lots and is independent of external bias networks when tested per the 2004 Philips specification.

Does BF423,112 have built-in protection features such as thermal shutdown or overcurrent limiting?

No, BF423,112 is a discrete bipolar junction transistor without any integrated protection circuitry. It relies entirely on external design measures - including base current limiting, heatsinking, and voltage clamping - to prevent thermal runaway or secondary breakdown. The datasheet specifies no internal diodes, fuses, or sensing elements; all protection must be implemented at the PCB level per IEC 60134 limiting values.

What is the thermal resistance from junction to ambient (Rth(j-a)) for BF423,112?

The thermal resistance from junction to ambient (Rth(j-a)) for BF423,112 is 150 K/W, measured with the transistor mounted on a printed-circuit board per the 2004 Philips datasheet note. This value assumes standard FR-4 PCB with minimal copper area and defines the temperature rise per watt of dissipated power. For reliable operation near 830 mW Ptot, additional copper pour or thermal vias are recommended to reduce effective Rth(j-a).