onsemi BC373G

Overview

BC373G 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, and P_D = 1.5 W at T_A = 25°C. It delivers h_FE ≥ 8.0 (min) at I_C = 100 mA, V_CE = 5 V, and exhibits V_CE(sat) ≤ 1.1 V at I_C = 250 mA / I_B = 0.25 mA - suited for medium-power switching in industrial relay drivers and lamp ballasts.

For engineers reviewing the BC373G datasheet, pinout, applications, or equivalent options, key selection criteria include verified V_CEO/V_CES = 80 V rating, Darlington gain structure, TO-92 thermal resistance (R_JA = 200 °C/W), and Pb-free compliance per ON Semiconductor's Rev. 3 specification.

Technical Context

The BC373G implements a monolithic NPN Darlington pair with integrated base-emitter shunt resistor absent - requiring external base drive control. Its high V_CEO and V_CES ratings (80 V) support operation in inductive load circuits up to 60 V bus voltage with margin.

It features f_T = 100–200 MHz at I_C = 100 mA, V_CE = 5 V, enabling use in low-frequency switching (≤100 kHz) with fast turn-off capability; Cob = 10–25 pF at V_CB = 10 V ensures minimal Miller effect in driver stages.

Key Specifications

Pinout & Package

BC373G is housed in a standard TO-92 (Case 29-11) plastic package with 3 leads, lead-free finish, and JEDEC-compliant dimensions (A = 4.45–5.20 mm, B = 4.32–5.33 mm). Thermal resistance R_JA = 200 °C/W reflects natural convection performance on FR-4 PCB without copper pour.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC373G, BC373ZL1G offers identical performance in a different packaging format ideal for pick-and-place, while MJD127G provides higher power handling at the cost of board area and layout redesign - neither is pin-compatible, but both serve overlapping high-voltage switching roles.

Availability

BC373G is available at Aetrix Electronics and suitable for industrial relay drivers, AC lamp ballasts, DC motor starters, and power supply enable switches requiring stable component supply and RoHS-compliant sourcing.

Supply support for BC373G 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 part of onsemi) is a global semiconductor supplier specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC373G belongs to the BC37x family of high-voltage Darlington transistors designed for robust, cost-effective medium-power switching in industrial controls and appliance power stages.

FAQ

What is the maximum collector-emitter voltage rating for BC373G?

The BC373G has a guaranteed minimum V_CEO rating of 80 Vdc under specified test conditions (I_C = 100 µA, I_B = 0). This rating is validated per ON Semiconductor's Rev. 3 datasheet and applies to continuous DC operation with appropriate derating above 25°C ambient. Exceeding 80 V risks breakdown and permanent device failure.

Does BC373G include an internal base-emitter resistor?

No, the BC373G does not integrate a base-emitter shunt resistor. It is a standard two-terminal base-controlled Darlington transistor requiring external base current limiting. This differs from "digital transistor" variants like the NSBC114EPDWX, and confirms the need for discrete base resistor design per application requirements.

What is the thermal resistance junction-to-ambient for BC373G in TO-92 package?

The BC373G has R_JA = 200 °C/W when mounted on a standard FR-4 PCB with no copper pour, per ON Semiconductor's thermal characterization. This value assumes natural convection only; adding 1 in² of 2-oz copper pad reduces R_JA to approximately 120 °C/W, directly impacting safe continuous current limits.

Can BC373G replace BC372G in existing designs?

BC373G is not a drop-in replacement for BC372G due to its lower V_CEO and V_CES ratings (80 V vs. 100 V). While pinout and package are identical, substituting BC373G in a 100 V application risks premature breakdown. Use BC373G only where operating voltage remains ≤60 V with margin.

Is BC373G suitable for PWM motor control at 20 kHz?

Yes, the BC373G supports PWM motor control up to 20 kHz due to its f_T = 100–200 MHz and low Cob = 10–25 pF, which minimize switching losses and ensure clean turn-on/turn-off edges. However, V_CE(sat) increases slightly at higher frequencies, so thermal validation at full load duty cycle is recommended.