onsemi BC373RL1

Overview

BC373RL1 from onsemi is an NPN silicon high-voltage Darlington transistor in TO-92 package, rated for 80 V_CEO, 1.0 A continuous collector current, and 1.5 W power dissipation at T_A = 25°C. It delivers DC current gain (h_FE) of 8–160 at I_C = 100 mA, V_CE = 5 V, and supports switching applications requiring high current gain with low base drive, such as relay drivers and lamp controls.

For engineers reviewing the BC373RL1 datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO rating, h_FE consistency across temperature, V_CE(sat) at specified I_C/I_B, thermal resistance (R_JA = 200°C/W), and TO-92 mechanical compatibility in space-constrained linear/switching circuits.

Technical Context

The BC373RL1 implements a monolithic Darlington pair structure to achieve high current gain with minimal base drive-enabling direct interface with microcontroller GPIOs or logic-level signals. Its V_CEO = 80 V and V_CES = 80 V support operation in medium-voltage industrial control rails up to 60 V DC.

Thermal design is constrained by R_JA = 200°C/W and R_JC = 83.3°C/W, requiring careful PCB copper area allocation for heatsinking when operating near P_D = 1.5 W. The f_T = 100–200 MHz and C_ob = 10–25 pF indicate suitability for low-to-moderate frequency switching-not RF amplification.

Key Specifications

Pinout & Package

BC373RL1 is housed in a standard TO-92 (Case 29, Style 1) plastic package with straight leads and tape-and-reel packaging (2000 units/reel). Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector - verified per marking diagram and package outline drawing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC373RL1, BC373RL1G adds RoHS compliance without performance trade-offs, while BC372RL1 extends voltage headroom at no gain or thermal penalty-making BC373RL1 the optimal choice for cost-sensitive 24–48 V industrial switching where Pb-free is optional.

Availability

BC373RL1 is available at Aetrix Electronics and suitable for relay driver circuits, lamp switching, motor assist functions, and industrial sensor interfaces requiring stable component supply and long-term manufacturability.

Supply support for BC373RL1 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier focused on energy-efficient electronics, serving automotive, industrial, cloud, and consumer markets with discrete, analog, and logic solutions.

The BC373RL1 belongs to onsemi's general-purpose bipolar transistor family designed for robust, cost-effective linear and switching applications in industrial control, power management, and interface circuits.

FAQ

What is the maximum collector-emitter voltage rating for BC373RL1?

The BC373RL1 has a maximum collector-emitter voltage (V_CEO) rating of 80 Vdc, tested under I_C = 100 µA condition. This rating defines the absolute upper limit for voltage applied between collector and emitter with base open. Exceeding 80 V risks avalanche breakdown and permanent device failure. Designers should maintain at least 20% derating (≤64 V) for reliability in continuous operation.

Does BC373RL1 have a Pb-free version, and how does it differ?

Yes, BC373RL1G is the Pb-free version of BC373RL1, using lead-free plating on the same TO-92 package and identical silicon die. Electrical parameters-including V_CEO, h_FE, V_CE(sat), and thermal resistance-are fully matched. The only difference is RoHS/ELV compliance; BC373RL1G is required for lead-free soldering processes and environmental reporting, while BC373RL1 remains suitable for legacy SnPb assembly.

What is the typical DC current gain (hFE) of BC373RL1 at 100 mA collector current?

The BC373RL1 exhibits a DC current gain (h_FE) ranging from 8 to 160 at I_C = 100 mA and V_CE = 5 V, per the official onsemi datasheet. This wide spread reflects manufacturing tolerance; design must assume h_FE(min) = 8 for worst-case saturation analysis. At lower currents (e.g., 10 mA), h_FE typically rises to 50–120, improving base drive efficiency in low-power modes.

Can BC373RL1 be used in surface-mount designs?

No, BC373RL1 is exclusively offered in the through-hole TO-92 package (Case 29, Style 1) with straight or bent leads. It has no SMT variant. For surface-mount equivalents, consider onsemi's NSS series (e.g., NSS20501MR6T1G) or Diodes Inc.'s DXT373-13, which provide similar Darlington gain and voltage ratings in SOT-23 or SOT-89 packages-but require PCB redesign and validation of thermal performance.

What is the thermal resistance junction-to-ambient (RJA) for BC373RL1 in free-air conditions?

The BC373RL1 has a thermal resistance junction-to-ambient (R_JA) of 200°C/W when mounted on a standard FR-4 PCB with minimal copper (JEDEC standard test board). This value assumes no added heatsinking. To sustain 1.5 W dissipation, ambient temperature must remain below 40°C-or copper pour area increased significantly to reduce effective R_JA below 100°C/W for higher ambient operation.