NXP Semiconductors BC875,126

Overview

BC875,126 from Nexperia (formerly Philips Semiconductors) is an NPN Darlington transistor in a TO-92 (SOT54/SC-43A) through-hole package, delivering min. h_FE = 1000 at I_C = 150 mA, V_CE = 10 V, with V_CESAT ≤ 1.3 V at I_C = 0.5 A / I_B = 0.5 mA, and rated for 45 V V_CES and 1 A continuous collector current - used primarily as high-gain relay drivers in industrial control modules.

For engineers reviewing the BC875,126 datasheet, BC875,126 pinout, BC875,126 application, or BC875,126 equivalent, key selection considerations include its integrated base-emitter resistor-diode network, low saturation voltage under medium-current switching, thermal resistance of 150 K/W on FR4, and compatibility with legacy TO-92 PCB footprints requiring no layout revision.

Technical Context

The BC875,126 implements a monolithic NPN Darlington pair with built-in base-emitter clamping diode and series base resistor, enabling direct TTL/CMOS logic-level drive without external bias components. Its architecture supports high DC gain stability across I_C = 150 mA to 1 A while maintaining V_BESAT ≤ 2.2 V at full-rated current.

Designed for linear and switching operation up to f_T = 200 MHz, it exhibits t_ON ≤ 500 ns and t_OFF ≤ 1300 ns under defined test conditions (I_Con = 500 mA, I_Boff = −0.5 mA), with absolute maximum ratings including T_j = 150 °C and P_tot = 0.83 W at T_amb ≤ 25 °C on FR4.

Key Specifications

Pinout & Package

BC875,126 is housed in a plastic single-ended leaded (through-hole) TO-92 package designated SOT54 or SC-43A, with 3 leads and standardized 2.54 mm lead pitch. The package is compatible with manual soldering and wave-solder processes on FR4 boards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC875,126, BC879,126 extends voltage capability without altering drive or thermal behavior, while ULN2003AD1013TR trades single-device simplicity for multi-channel integration and SMT compatibility - neither is pin-compatible, but both serve overlapping relay-driving functions with distinct layout and system-level trade-offs.

Availability

BC875,126 is available at Aetrix Electronics and suitable for industrial relay drivers, low-voltage solenoid control, and automotive door lock actuator circuits requiring stable component supply and long-term obsolescence support.

Supply support for BC875,126 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

Nexperia - formerly Philips Semiconductors - is a global semiconductor expert focused on high-volume, high-reliability discrete and logic devices, with leadership in automotive-qualified and industrial-grade components.

The BC875,126 belongs to Nexperia's legacy bipolar transistor portfolio, engineered specifically for cost-sensitive, high-reliability electromechanical interface applications such as relay and solenoid driving in harsh ambient environments.

FAQ

What is the maximum continuous collector current rating for BC875,126?

The BC875,126 is rated for a maximum continuous collector current (I_C) of 1 A at T_amb ≤ 25 °C on FR4 PCB. Derating is required above 25 °C ambient - for example, at 70 °C ambient, usable I_C drops to approximately 0.6 A due to thermal limitations. Always verify actual board-level thermal performance using R_th(j-a) = 150 K/W and junction temperature limits (T_j ≤ 150 °C) in your specific layout.

Does BC875,126 include an integrated flyback diode?

Yes, the BC875,126 integrates a base-emitter clamping diode - confirmed in the "FEATURES" section of its Philips/Nexperia datasheet. This diode protects the base-emitter junction from reverse breakdown during inductive load switching (e.g., relay coils), but it does not replace an external flyback diode across the load itself. For full inductive energy dissipation, a separate flyback diode across the relay coil remains necessary.

Is BC875,126 pin-compatible with BC547 or BC337 transistors?

No, BC875,126 is not pin-compatible with BC547 or BC337. While all three use TO-92 packages, BC875,126 has Base–Collector–Emitter pinout (1–2–3), whereas BC547 and BC337 follow Emitter–Base–Collector (1–2–3). Swapping them without PCB modification will cause circuit failure. Always verify pin assignment using the official BC875,126 datasheet diagram before substitution.

What is the typical transition frequency (f_T) of BC875,126 and its design implication?

The BC875,126 has a typical transition frequency f_T of 200 MHz at V_CE = 5 V and I_C = 0.5 A. This indicates strong high-frequency current gain capability, supporting clean switching up to ~20 kHz PWM frequencies in relay/solenoid control. However, its Darlington structure introduces inherent storage delay - so while f_T is high, practical switching speed is governed more by t_OFF = 1300 ns than by f_T alone.

Can BC875,126 be used in surface-mount designs?

No, BC875,126 is a through-hole device in TO-92 (SOT54/SC-43A) package and is not suitable for standard surface-mount assembly. It lacks gull-wing or J-lead terminations and requires plated-through holes. For SMT equivalents, consider Nexperia's PBSS4041T (SOT23) or the 7-channel ULN2003A (SO-16), both offering Darlington functionality in surface-mount formats - but with different pinouts and electrical characteristics than BC875,126.