BC373 Equivalent & Substitute Parts

Part Overview

The BC373 is an NPN Darlington bipolar junction transistor manufactured by onsemi, designed for general-purpose switching and amplification applications. This device features an 80 V collector-emitter breakdown voltage rating and a maximum collector current of 1 A, housed in a TO-92 through-hole package. The BC373 is classified as obsolete, making identification of functionally equivalent alternatives necessary for ongoing design support and production continuity. Substitute parts must maintain electrical compatibility across critical parameters including voltage ratings, current capacity, and thermal operating range while accommodating modern component availability and compliance requirements.

Substiute Parts

BC373

onsemiIn Stock: 974BC373 Datasheet

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ZTX603

Diodes IncorporatedIn Stock: 2132ZTX603 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the BC373 are identified based on strict electrical and mechanical parameter alignment. The substitution criteria are:

Mandatory Matching Parameters:

• Transistor Type: NPN - Darlington configuration
• Current - Collector (Ic) (Max): 1 A minimum
• Voltage - Collector Emitter Breakdown (Max): 80 V minimum
• Mounting Type: Through Hole
• Package Compatibility: TO-92 or TO-92 compatible form factor

Acceptable Parameter Variations:

• Vce Saturation: May be lower (improved performance)
• DC Current Gain (hFE): May be lower (acceptable for switching applications)
• Power Dissipation: May be higher (provides design margin)
• Frequency - Transition: May be lower (acceptable for general-purpose applications)
• Operating Temperature Range: May be wider (provides extended operating envelope)
• Product Status: Active status preferred for long-term availability

The ZTX603 meets all mandatory matching criteria and qualifies as a direct electrical substitute.

Parameter Comparison

Engineering Selection Recommendations

ZTX603 Substitution Assessment:

The ZTX603 manufactured by Diodes Incorporated is a qualified direct substitute for the BC373. This determination is based on the following factors:

Electrical Compatibility: The ZTX603 maintains identical maximum ratings for collector current (1 A) and collector-emitter breakdown voltage (80 V). Both devices are NPN Darlington transistors with through-hole mounting, ensuring functional equivalence in switching and amplification circuits designed for the BC373.

Product Status Advantage: The ZTX603 carries Active product status, providing assured long-term availability and supply chain continuity. The BC373 is classified as Obsolete, making the ZTX603 the preferred selection for new designs and production continuity.

Compliance and Certification: The ZTX603 is RoHS3 compliant, meeting current environmental and regulatory requirements. Both devices maintain REACH Unaffected status and EAR99 export classification.

Thermal Operating Range: The ZTX603 extends the upper operating temperature limit to 200°C (compared to 150°C for BC373), providing enhanced thermal margin for applications requiring elevated temperature operation.

Power Dissipation: The ZTX603 offers 1 W maximum power dissipation versus 625 mW for the BC373, providing additional thermal headroom in power-limited applications.

Package Compatibility: The ZTX603 E-Line package is mechanically and electrically compatible with TO-92 footprints, enabling direct board-level substitution without layout modifications.

Frequently Asked Questions (FAQ)

Q: Can the ZTX603 be used as a direct replacement for the BC373 in existing designs?

A: Yes. The ZTX603 is electrically and mechanically compatible with the BC373. Both devices share identical maximum ratings for collector current (1 A) and collector-emitter breakdown voltage (80 V), and both employ NPN Darlington configuration in through-hole TO-92 compatible packages. No circuit modifications are required for substitution.

Q: What are the key differences between the BC373 and ZTX603?

A: The primary differences are product status, compliance, and thermal specifications. The ZTX603 is Active (versus Obsolete for BC373), RoHS3 compliant, and rated for operation to 200°C (versus 150°C). The ZTX603 also provides higher power dissipation (1 W versus 625 mW). These differences favor the ZTX603 for new designs and long-term production.

Q: Are there any performance trade-offs when substituting the ZTX603 for the BC373?

A: The ZTX603 exhibits lower DC current gain (2000 @ 1A, 5V versus 10000 @ 100mA, 5V) and lower transition frequency (150MHz versus 200MHz). For general-purpose switching applications, these differences are not limiting. Applications requiring maximum current gain or high-frequency operation should be evaluated against specific circuit requirements.

Q: Is the ZTX603 package footprint identical to the BC373?

A: The ZTX603 uses an E-Line package that is TO-92 compatible. Both devices are through-hole components with three leads. The E-Line package maintains mechanical and electrical compatibility with standard TO-92 PCB footprints, enabling direct substitution without layout changes.

Q: What is the moisture sensitivity level for both devices?

A: Both the BC373 and ZTX603 carry MSL 1 (Unlimited) classification, indicating no moisture sensitivity restrictions. Standard handling and storage procedures apply.

Q: Are there any RoHS or environmental compliance considerations?

A: The BC373 is RoHS non-compliant. The ZTX603 is RoHS3 compliant, meeting current environmental regulations. Both devices are REACH Unaffected and carry EAR99 export classification.