onsemi BC373ZL1

Overview

BC373ZL1 from ON Semiconductor is an NPN silicon high-voltage Darlington transistor in TO-92 package, rated for V_CEO = 80 V, I_C = 1.0 A, P_D = 1.5 W at T_A = 25°C, with h_FE ≥ 8.0 (min) at I_C = 100 mA and V_CE = 5 V. It serves as a medium-power switching or amplification device in relay drivers, power supplies, and lamp controls.

For engineers reviewing the BC373ZL1 datasheet, pinout, applications, or equivalent options, key selection criteria include its 80 V V_CEO, 1.5 W power dissipation capability, Darlington gain structure, TO-92 mechanical compatibility, and 100–200 MHz f_T bandwidth performance.

Technical Context

The BC373ZL1 implements a monolithic NPN Darlington pair with integrated base-emitter resistor network absent-external base drive is required. Its high DC current gain (h_FE up to 160) enables low-base-current switching control while maintaining V_CE(sat) ≤ 1.1 V at I_C = 250 mA and I_B = 0.25 mA.

Thermal design relies on R_JA = 200°C/W and R_JC = 83.3°C/W, supporting operation from −55°C to +150°C junction temperature. Dynamic behavior includes C_ob = 10–25 pF and f_T = 100–200 MHz, confirming suitability for medium-speed switching-not RF amplification.

Key Specifications

Pinout & Package

BC373ZL1 uses the standard TO-92 (Case 29-11, Style 1) plastic package with 3 leads, 4.45–5.20 mm body height, and 2.54 mm lead pitch. Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC373ZL1, BC373RL1 offers identical performance in tape-and-reel format for automated assembly, while MJD127G delivers higher power handling in TO-220 but requires layout redesign and thermal management-neither is pin-compatible.

Availability

BC373ZL1 is available at Aetrix Electronics and suitable for relay drivers, small DC motor controls, lamp switching, and industrial power supply sequencing requiring stable component supply and Pb-free compliance.

Supply support for BC373ZL1 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, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC373ZL1 belongs to the BC37x family of high-voltage Darlington transistors designed for cost-sensitive, medium-power linear and switching applications where gain, voltage margin, and TO-92 compatibility are prioritized over ultra-high speed or RF performance.

FAQ

What is the maximum collector-emitter voltage rating for BC373ZL1?

The BC373ZL1 has a maximum collector-emitter voltage (V_CEO) rating of 80 V DC. This specification defines the highest voltage that can be applied between collector and emitter with the base open before breakdown occurs. Engineers must ensure operating voltage margins stay below this limit, especially considering transient spikes in inductive load switching. The BC373ZL1's 80 V rating makes it suitable for 24 V and 48 V industrial systems with safety headroom.

Does BC373ZL1 have a built-in base-emitter resistor?

No, the BC373ZL1 does not include an integrated base-emitter resistor. It is a standard two-lead Darlington transistor (base and emitter externally accessible), requiring external base drive circuitry. Unlike "digital transistors" such as the NSBC114, the BC373ZL1 relies on discrete resistors or active drivers to set base current. This gives designers full control over gain and switching speed but adds one external component versus resistor-equipped variants.

What is the thermal resistance from junction to ambient for BC373ZL1?

The BC373ZL1 has a thermal resistance from junction to ambient (R_JA) of 200°C/W when mounted on a standard FR-4 PCB with no heatsink. This value assumes typical TO-92 mounting conditions per the datasheet. At 1.0 A collector current and 1.1 V saturation voltage, power dissipation reaches ~1.1 W-requiring significant derating above 25°C ambient. For sustained operation, ambient temperature must remain below ~70°C or supplemental airflow/heatsinking applied.

Is BC373ZL1 RoHS-compliant and Pb-free?

Yes, BC373ZL1 is RoHS-compliant and Pb-free. The "ZL1" suffix denotes the ammo-pack packaging variant of the Pb-free version (equivalent to BC373G). ON Semiconductor documents this in the ordering information table, confirming compliance with EU RoHS Directive 2011/65/EU. No lead content is present in the die, bond wires, or TO-92 mold compound, making BC373ZL1 suitable for environmentally regulated industrial and consumer products.

How does BC373ZL1 differ from BC372 in practical use?

The BC373ZL1 differs from BC372 primarily in voltage ratings: BC373ZL1 has V_CEO = 80 V and V_CES = 80 V, whereas BC372 is rated for 100 V in both parameters. All other specifications-including I_C, P_D, h_FE, and package-are identical. Therefore, BC373ZL1 is selected when 80 V margin suffices and cost or inventory consolidation favors the BC373 variant; BC372 remains preferred for designs requiring >80 V transient tolerance.