KSC5021RTU Equivalent & Substitute Parts

Part Overview

The KSC5021RTU is an NPN bipolar junction transistor manufactured by onsemi, rated for 500 V collector-emitter breakdown voltage and 5 A maximum collector current in a Through Hole TO-220-3 package. This device is classified as obsolete, making identification of equivalent substitute components necessary for ongoing design support, maintenance, and production continuity. The KSC5021RTU delivers 50 W maximum power dissipation with an 18 MHz transition frequency, suitable for general-purpose switching and amplification applications in industrial and consumer electronics.

Substiute Parts

KSC5021RTU

onsemiIn Stock: 995KSC5021RTU Datasheet

Current PartRFQ

BUJ303A,127

WeEn SemiconductorsIn Stock: 6631BUJ303A,127 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the KSC5021RTU is determined by strict equivalence across the following electrical and mechanical parameters:

Critical Matching Parameters:

• Transistor polarity: NPN
• Voltage rating: 500 V collector-emitter breakdown (maximum)
• Current rating: 5 A maximum collector current
• Package type: TO-220-3 Through Hole mounting
• Operating temperature range: 150°C maximum junction temperature

Allowable Variation Parameters:

• Power dissipation: Substitute may exceed 50 W maximum (higher power rating is acceptable)
• Vce saturation: Substitute may differ within the specified operating point
• DC current gain (hFE): Substitute may differ at specified test conditions
• Collector cutoff current (ICBO): Substitute may differ
• Transition frequency: Substitute may differ or be unspecified

The BUJ303A,127 manufactured by WeEn Semiconductors meets all critical matching parameters and is therefore classified as a direct substitute for the KSC5021RTU.

Parameter Comparison

Engineering Selection Recommendations

The BUJ303A,127 is a qualified substitute for the KSC5021RTU based on the following engineering criteria:

Electrical Compatibility: Both devices share identical voltage and current ratings (500 V, 5 A), ensuring functional equivalence in circuit applications. The BUJ303A,127 provides higher power dissipation capability (100 W versus 50 W), which presents no compatibility constraint and may offer improved thermal margin in applications approaching the original device's power limits.

Regulatory Compliance: Both the KSC5021RTU and BUJ303A,127 carry ROHS3 compliance and REACH Unaffected status, satisfying environmental and regulatory requirements for equivalent use.

Product Availability: The KSC5021RTU is classified as obsolete, while the BUJ303A,127 maintains active product status with 6581 units in stock. This availability differential supports the substitution for new designs and ongoing production requirements.

Package Compatibility: Both devices utilize Through Hole TO-220-3 packaging, ensuring mechanical and thermal interface compatibility with existing PCB layouts and heatsink assemblies.

Secondary Parameter Variations: Differences in Vce saturation, collector cutoff current, and DC current gain fall within acceptable tolerance ranges for general-purpose switching applications. The unspecified transition frequency of the BUJ303A,127 does not preclude substitution in applications where the original 18 MHz specification is not a critical design constraint.

Frequently Asked Questions (FAQ)

Q: Can the BUJ303A,127 be used as a direct replacement for the KSC5021RTU in existing designs?

A: Yes. The BUJ303A,127 meets all critical electrical and mechanical parameters: 500 V breakdown voltage, 5 A collector current, NPN polarity, and TO-220-3 Through Hole package. No circuit modifications are required for substitution.

Q: What is the significance of the higher power rating (100 W) on the BUJ303A,127?

A: The higher power dissipation rating of the BUJ303A,127 (100 W versus 50 W) indicates greater thermal capability. This does not create incompatibility; it simply means the substitute device can handle higher power levels without thermal stress. Existing designs operating within the original 50 W specification remain fully compatible.

Q: How do the differences in Vce saturation affect circuit performance?

A: The BUJ303A,127 exhibits 1.5 V saturation voltage compared to 1 V for the KSC5021RTU at the specified test point (600 mA base current, 3 A collector current). This 0.5 V difference is typical among NPN transistor variants and does not preclude substitution in general-purpose switching circuits. Applications with strict saturation voltage requirements should conduct circuit-level analysis.

Q: Why is the transition frequency unspecified for the BUJ303A,127?

A: The transition frequency specification is not provided in the BUJ303A,127 datasheet parameters. For applications where switching speed is not a critical design parameter, this omission does not affect substitution validity. Applications requiring specific frequency performance should consult the complete manufacturer datasheet.

Q: Are there any thermal management differences between these devices?

A: Both devices are rated for 150°C maximum junction temperature and use identical TO-220-3 Through Hole packaging. Thermal management approaches remain unchanged. The higher power rating of the BUJ303A,127 may provide additional thermal margin in thermally constrained applications.

Q: What is the inventory status for each device?

A: The KSC5021RTU has 967 units in stock but is classified as obsolete, indicating no future production. The BUJ303A,127 has 6581 units in stock and maintains active product status, ensuring long-term availability for new designs and production continuity.

Q: Are both devices compliant with environmental regulations?

A: Yes. Both the KSC5021RTU and BUJ303A,127 are ROHS3 compliant and REACH Unaffected, meeting current environmental and regulatory requirements for electronic component use.