BC237CG Equivalent & Substitute Parts

Part Overview

The BC237CG is an NPN bipolar junction transistor manufactured by onsemi, rated for 45V collector-emitter breakdown voltage and 100mA maximum collector current. This device is packaged in a TO-92 (TO-226-3) through-hole configuration and is classified as obsolete. Due to its obsolete status, equivalent substitute parts with active product status are necessary for new designs and ongoing production requirements. The BC237CG remains available in inventory (1130 pieces), but substitutes provide access to active product lines with extended support and compliance certifications.

Substiute Parts

BC237CG

onsemiIn Stock: 1141BC237CG Datasheet

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ZTX450

Diodes IncorporatedIn Stock: 1682ZTX450 Datasheet

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ZTX690B

Diodes IncorporatedIn Stock: 1864ZTX690B Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the BC237CG is determined by the following critical parameters that must be maintained or exceeded:

Mandatory Matching Parameters:

• Transistor Type: NPN
• Voltage - Collector Emitter Breakdown (Max): 45 V (minimum requirement)
• Mounting Type: Through Hole
• Package Compatibility: TO-92 or TO-92 compatible form factor

Performance Parameters (Allowable Upgrades):

• Current - Collector (Ic) (Max): 100 mA minimum (upgrades permitted)
• Power - Max: 350 mW minimum (upgrades permitted)
• Frequency - Transition: 200 MHz minimum (upgrades permitted)
• Operating Temperature Range: Must encompass -55°C to 150°C minimum

The substitute parts ZTX450 and ZTX690B meet or exceed all mandatory parameters while providing enhanced electrical performance characteristics and active product status with RoHS3 compliance.

Parameter Comparison

Engineering Selection Recommendations

ZTX450 Selection Criteria: The ZTX450 is suitable for applications requiring collector current up to 1A with 45V breakdown voltage. This substitute provides a 10x increase in maximum collector current capability while maintaining the 45V voltage rating. The ZTX450 features active product status, RoHS3 compliance, and extended operating temperature range to 200°C. The E-Line package is mechanically and electrically compatible with TO-92 form factor applications. Transition frequency is reduced to 150MHz, which is acceptable for applications not requiring the full 200MHz bandwidth of the BC237CG.

ZTX690B Selection Criteria: The ZTX690B is suitable for applications requiring collector current up to 2A with 45V breakdown voltage. This substitute provides a 20x increase in maximum collector current capability while maintaining the 45V voltage rating. The ZTX690B features active product status, RoHS3 compliance, and extended operating temperature range to 200°C. The E-Line package is mechanically and electrically compatible with TO-92 form factor applications. Transition frequency is reduced to 150MHz, which is acceptable for applications not requiring the full 200MHz bandwidth of the BC237CG.

Compliance Considerations: Both substitute parts carry RoHS3 compliance certification and REACH Unaffected status, providing regulatory alignment for current manufacturing standards. The BC237CG, as an obsolete component, lacks these modern compliance certifications.

Frequently Asked Questions (FAQ)

Q: Can the ZTX450 or ZTX690B be used as direct pin-for-pin replacements for the BC237CG?

A: Yes. Both substitute parts are packaged in E-Line-3 form factor, which is mechanically and electrically compatible with TO-92-3 through-hole applications. Pin configuration and polarity are identical. Physical dimensions allow direct substitution in existing PCB layouts designed for TO-92 packages.

Q: What is the primary difference between ZTX450 and ZTX690B?

A: The primary difference is maximum collector current rating. The ZTX450 is rated for 1A maximum collector current, while the ZTX690B is rated for 2A maximum collector current. Both maintain the 45V breakdown voltage specification. Selection depends on the specific current requirements of the application.

Q: Why is the transition frequency lower in the substitute parts?

A: The ZTX450 and ZTX690B are rated for 150MHz transition frequency compared to the BC237CG's 200MHz. This reduction is acceptable for most general-purpose switching and amplification applications. Applications requiring frequencies above 150MHz should retain the BC237CG or evaluate alternative high-frequency transistor options.

Q: Are there any thermal considerations when substituting these parts?

A: The substitute parts support extended operating temperature range to 200°C compared to the BC237CG's 150°C maximum. Both substitute parts feature 1W maximum power dissipation compared to the BC237CG's 350mW. Thermal design margins improve with the substitute parts due to higher power ratings.

Q: What is the significance of the E-Line package designation?

A: E-Line is a through-hole package format manufactured by Diodes Incorporated that maintains mechanical and electrical compatibility with standard TO-92 packages. The E-Line-3 designation indicates a three-lead configuration matching the collector, base, and emitter pin arrangement of the BC237CG.

Q: How do the saturation voltage characteristics compare?

A: The ZTX450 exhibits lower saturation voltage (250mV) compared to the BC237CG (600mV) at comparable current levels, indicating improved switching efficiency. The ZTX690B saturation voltage (500mV) is intermediate. Lower saturation voltage reduces power dissipation in switching applications.

Q: Are the substitute parts suitable for high-frequency switching applications?

A: The 150MHz transition frequency of both substitute parts supports switching applications up to approximately 50MHz practical frequency. Applications requiring switching frequencies above this range should evaluate the BC237CG's 200MHz specification or select alternative high-frequency transistor families.