KSC2518R Equivalent & Substitute Parts

Part Overview

The KSC2518R is an NPN bipolar junction transistor manufactured by onsemi, rated for 400 V collector-emitter breakdown voltage and 4 A maximum collector current in a TO-220-3 through-hole package. This device is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. The 40 W power rating and saturation characteristics position this transistor for general-purpose switching and amplification applications in power electronics.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	400	V
Current - Collector (Ic) (Max)	4	A
Power - Max	40	W
Vce Saturation (Max) @ Ib, Ic	1 V @ 300 mA, 1.5 A	—
DC Current Gain (hFE) (Min) @ Ic, Vce	20 @ 300 mA, 5 V	—
Current - Collector Cutoff (Max)	10	µA
Operating Temperature (TJ)	150	°C
Package / Case	TO-220-3	—
Mounting Type	Through Hole	—

Substitute Part Grouping Explanation

Substitution of the KSC2518R is determined by electrical and mechanical compatibility within the following criteria:

Primary Substitution Parameters:

Transistor Type: NPN (required match)
Package / Case: TO-220-3 (required match for mechanical compatibility)
Mounting Type: Through Hole (required match)
Voltage - Collector Emitter Breakdown (Max): minimum 400 V
Current - Collector (Ic) (Max): minimum 4 A
Operating Temperature (TJ): minimum 150 °C

Secondary Compatibility Factors:

Power dissipation rating of 40 W or greater
Vce saturation characteristics suitable for switching applications
DC current gain (hFE) characteristics within application tolerance

Substitute parts are grouped into two categories based on electrical ratings:

Category A - Direct Electrical Match (400 V, 4 A): BUL128D-B, BUL742C, ST13005. These parts maintain the exact voltage and current specifications of the KSC2518R with enhanced power ratings and active product status.

Category B - Enhanced Electrical Ratings (450 V, 5 A): BUL38D, BUL49D. These parts exceed the KSC2518R specifications, providing higher voltage and current margins suitable for applications requiring additional design headroom.

Category C - Marginal Voltage Match (420 V, 5 A): TSC742CZ C0G. This part slightly exceeds voltage specification with enhanced current rating.

Parameter Comparison

Parameter	KSC2518R	BUL128D-B	BUL742C	ST13005	BUL38D	BUL49D	TSC742CZ C0G
Manufacturer	onsemi	STMicroelectronics	STMicroelectronics	STMicroelectronics	STMicroelectronics	STMicroelectronics	Taiwan Semiconductor
Product Status	Obsolete	Active	Active	Active	Active	Active	Active
Transistor Type	NPN	NPN	NPN	NPN	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	400 V	400 V	400 V	400 V	450 V	450 V	420 V
Current - Collector (Ic) (Max)	4 A	4 A	4 A	4 A	5 A	5 A	5 A
Power - Max	40 W	70 W	70 W	75 W	80 W	80 W	70 W
Vce Saturation (Max) @ Ib, Ic	1 V @ 300 mA, 1.5 A	500 mV @ 1 A, 4 A	1.5 V @ 1 A, 3.5 A	1 V @ 1 A, 4 A	1.1 V @ 750 mA, 3 A	1.2 V @ 800 mA, 4 A	1.5 V @ 1 A, 3.5 A
Current - Collector Cutoff (Max)	10 µA	250 µA	250 µA	1 mA	250 µA	100 µA	250 µA
DC Current Gain (hFE) (Min) @ Ic, Vce	20 @ 300 mA, 5 V	12 @ 2 A, 5 V	25 @ 800 mA, 3 V	8 @ 2 A, 5 V	10 @ 10 mA, 5 V	4 @ 7 A, 10 V	48 @ 100 mA, 5 V
Operating Temperature (TJ)	150 °C	150 °C	150 °C	150 °C	150 °C	150 °C	150 °C
Package / Case	TO-220-3	TO-220-3	TO-220-3	TO-220-3	TO-220-3	TO-220-3	TO-220-3
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
RoHS Status	—	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

For Direct Replacement (Equivalent Electrical Performance):

BUL742C is the primary substitute for the KSC2518R. This STMicroelectronics part maintains identical voltage (400 V) and current (4 A) ratings with 70 W power dissipation. The device is in active production status with ROHS3 compliance and REACH unaffected designation. DC current gain of 25 @ 800 mA, 3 V provides comparable switching characteristics. Inventory availability of 25,200 units supports production continuity.

ST13005 provides an alternative direct replacement with 400 V, 4 A specifications and 75 W power rating. This part offers lower collector cutoff current (1 mA) and is suitable for applications requiring reduced leakage. Active product status and ROHS3 compliance ensure long-term availability.

BUL128D-B offers the lowest Vce saturation (500 mV @ 1 A, 4 A) among direct replacements, making it suitable for applications prioritizing reduced power dissipation in saturation. The 70 W power rating and active status support production requirements.

For Enhanced Margin Applications:

BUL38D and BUL49D provide 450 V voltage rating and 5 A current capability, offering 12.5% voltage margin and 25% current margin over the KSC2518R specifications. Both parts are in active production with ROHS3 compliance. These devices are suitable for applications where design headroom is required or where the KSC2518R specifications represent minimum requirements.

For Marginal Voltage Tolerance Applications:

TSC742CZ C0G from Taiwan Semiconductor Corporation provides 420 V voltage rating with 5 A current capability. This part is in active production status with ROHS3 compliance. The 48 @ 100 mA, 5 V DC current gain provides enhanced switching speed characteristics. Moisture sensitivity level of 3 (168 hours) requires controlled storage conditions compared to level 1 for other substitutes.

Frequently Asked Questions (FAQ)

Q: Can BUL38D or BUL49D be used as direct replacements for KSC2518R?

A: Yes. Both parts meet or exceed all electrical requirements of the KSC2518R. The 450 V voltage rating and 5 A current rating provide margin above the 400 V, 4 A specifications. Mechanical compatibility is maintained through identical TO-220-3 packaging and through-hole mounting. These parts are suitable for applications where the KSC2518R specifications represent minimum design requirements.

Q: What is the difference between BUL742C and ST13005?

A: Both parts maintain 400 V, 4 A electrical specifications identical to the KSC2518R. BUL742C provides 70 W power dissipation with Vce saturation of 1.5 V @ 1 A, 3.5 A. ST13005 provides 75 W power dissipation with Vce saturation of 1 V @ 1 A, 4 A and lower collector cutoff current (1 mA versus 250 µA). ST13005 is preferred for applications requiring reduced leakage current or higher power dissipation capability.

Q: Is TSC742CZ C0G compatible with the KSC2518R?

A: TSC742CZ C0G is mechanically and functionally compatible. The part provides 420 V voltage rating (20 V above KSC2518R specification) and 5 A current rating (1 A above specification). Moisture sensitivity level 3 (168 hours) requires controlled storage and handling compared to level 1 for other substitutes. This part is suitable for applications where the enhanced current rating is beneficial.

Q: Why is BUL128D-B recommended as a substitute?

A: BUL128D-B maintains exact electrical specifications (400 V, 4 A) with 70 W power rating. The lowest Vce saturation value (500 mV @ 1 A, 4 A) among direct replacements reduces power dissipation during saturation operation. Active production status and high inventory availability (3,803 units) support production continuity. ROHS3 compliance and REACH unaffected status meet regulatory requirements.

Q: Are all substitute parts ROHS3 compliant?

A: All substitute parts listed are ROHS3 compliant except the original KSC2518R, which does not specify RoHS status. All parts maintain REACH unaffected designation. TSC742CZ C0G has moisture sensitivity level 3 (168 hours) while other substitutes have level 1 (unlimited).

Q: What is the primary consideration when selecting between substitute parts?

A: The primary consideration is application-specific power dissipation and switching speed requirements. For applications matching the original 400 V, 4 A specifications, BUL742C, ST13005, or BUL128D-B provide direct replacement. For applications requiring voltage or current margin, BUL38D or BUL49D are appropriate. Vce saturation characteristics determine power loss during switching operation and should be evaluated against thermal design constraints.

Q: Can substitute parts be used interchangeably in existing designs?

A: All substitute parts maintain TO-220-3 through-hole packaging and identical pinout compatibility. Electrical parameter variations, particularly Vce saturation and DC current gain, may affect circuit performance. Circuit simulation or prototype testing is appropriate when substituting parts with significantly different saturation characteristics or current gain values.

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