KSP42BU Equivalent & Substitute Parts

Part Overview

The KSP42BU is an NPN bipolar junction transistor manufactured by onsemi, rated for 300 V collector-emitter breakdown voltage and 500 mA maximum collector current. This through-hole TO-92-3 package device is designed for general-purpose switching and amplification applications requiring moderate voltage and current handling. The part maintains active product status with ROHS3 compliance and extensive inventory availability. Substitute parts are identified to address packaging preferences, extended temperature ranges, enhanced power dissipation capabilities, or regional supplier availability while maintaining core electrical performance parameters.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	300	V
Current - Collector (Ic) (Max)	500	mA
Power - Max	625	mW
Frequency - Transition	50	MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	40 @ 30mA, 10V	—
Vce Saturation (Max) @ Ib, Ic	500mV @ 2mA, 20mA	—
Current - Collector Cutoff (Max)	100	nA
Operating Temperature (Max)	150	°C
Mounting Type	Through Hole	—
Package / Case	TO-92-3	—

Substitute Part Grouping Explanation

Substitute parts for the KSP42BU are classified into two categories based on electrical and mechanical compatibility:

Parametric Equivalents maintain identical or equivalent electrical specifications across all critical parameters: 300 V collector-emitter breakdown voltage, 500 mA maximum collector current, 625 mW power dissipation, 50 MHz transition frequency, and 40 minimum DC current gain at specified conditions. These parts differ primarily in packaging format (Cut Tape, Box) or operating temperature range extensions. Parametric equivalents include MPSA42 and MPSA42BK.

Similar Alternatives share the core voltage and current ratings (300 V, 500 mA) and NPN transistor type but exhibit enhanced performance in secondary parameters such as increased power dissipation (1 W), higher transition frequency (75 MHz for ZTX457), or extended operating temperature ranges (-55°C to 200°C). These parts maintain through-hole mounting compatibility via E-Line package format (TO-92 compatible) and are suitable for applications where improved thermal performance or frequency response provides design margin. Similar alternatives include ZTX457 and ZTX657STZ.

Parameter Comparison

Parameter	KSP42BU	MPSA42	MPSA42BK	ZTX457	ZTX657STZ
Manufacturer	onsemi	Diotec Semiconductor	Diotec Semiconductor	Diodes Incorporated	Diodes Incorporated
Transistor Type	NPN	NPN	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	300 V	300 V	300 V	300 V	300 V
Current - Collector (Ic) (Max)	500 mA	500 mA	500 mA	500 mA	500 mA
Power - Max	625 mW	625 mW	625 mW	1 W	1 W
Frequency - Transition	50 MHz	50 MHz	50 MHz	75 MHz	30 MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	40 @ 30mA, 10V	40 @ 30mA, 10V	40 @ 30mA, 10V	50 @ 50mA, 10V	50 @ 100mA, 5V
Vce Saturation (Max) @ Ib, Ic	500mV @ 2mA, 20mA	500mV @ 2mA, 20mA	500mV @ 2mA, 20mA	300mV @ 10mA, 100mA	500mV @ 10mA, 100mA
Current - Collector Cutoff (Max)	100 nA	100 nA	100 nA	100 nA	100 nA
Operating Temperature (Max)	150°C	150°C	150°C	200°C	200°C
Operating Temperature (Min)	—	-55°C	-55°C	-55°C	-55°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	TO-92-3	TO-92-3	TO-92-3	E-Line-3	E-Line-3
RoHS Status	ROHS3 Compliant	Not applicable	Not applicable	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	Vendor Undefined	Vendor Undefined	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

MPSA42 and MPSA42BK Selection: These Diotec Semiconductor parts provide parametric equivalence to the KSP42BU across all primary electrical specifications. MPSA42 is supplied in Cut Tape packaging, while MPSA42BK is supplied in Box packaging. Both parts support the extended operating temperature range of -55°C to 150°C. Selection between these options depends on packaging and supply chain requirements. Note that RoHS and REACH compliance status differs from the KSP42BU; verify compliance requirements for your application.

ZTX457 Selection: This Diodes Incorporated part maintains the 300 V / 500 mA core ratings while providing enhanced performance through 1 W power dissipation (versus 625 mW) and 75 MHz transition frequency (versus 50 MHz). The extended operating temperature range to 200°C and ROHS3 compliance with REACH Unaffected status align with the KSP42BU compliance profile. The E-Line package format is mechanically compatible with TO-92 footprints. Selection is appropriate for applications requiring improved thermal margin or higher frequency operation.

ZTX657STZ Selection: This Diodes Incorporated part also maintains 300 V / 500 mA ratings with 1 W power dissipation and extended temperature range to 200°C. The 30 MHz transition frequency is lower than the KSP42BU baseline. ROHS3 compliance and REACH Unaffected status match the main part. The E-Line package format is mechanically compatible with TO-92 footprints. Selection is appropriate when thermal performance enhancement is required without frequency performance demands.

All substitute parts maintain active product status and demonstrate adequate inventory availability for production applications.

Frequently Asked Questions (FAQ)

Q: Can MPSA42 directly replace KSP42BU in existing designs?

A: MPSA42 provides parametric equivalence across all critical electrical specifications: 300 V breakdown voltage, 500 mA collector current, 625 mW power dissipation, 50 MHz transition frequency, and 40 minimum DC current gain. Both parts use TO-92-3 package format with identical pinout. Direct substitution is supported from an electrical and mechanical standpoint. Verify compliance documentation requirements for your application, as RoHS and REACH status differs between manufacturers.

Q: What is the difference between MPSA42 and MPSA42BK?

A: Both parts are manufactured by Diotec Semiconductor and provide identical electrical specifications. The primary difference is packaging format: MPSA42 is supplied in Cut Tape (CT) format, while MPSA42BK is supplied in Box format. Selection depends on your procurement and assembly process requirements. Both support the -55°C to 150°C operating temperature range.

Q: When should ZTX457 be selected over MPSA42?

A: ZTX457 is selected when applications require enhanced thermal performance or higher frequency operation. ZTX457 provides 1 W power dissipation (versus 625 mW in MPSA42) and 75 MHz transition frequency (versus 50 MHz). The extended operating temperature range to 200°C provides additional thermal margin. The E-Line package is mechanically compatible with TO-92 footprints. Select ZTX457 for designs operating near thermal or frequency limits.

Q: Are E-Line packages mechanically compatible with TO-92 footprints?

A: Yes. ZTX457 and ZTX657STZ use E-Line-3 package format specified as TO-92 compatible with formed leads. These parts are designed for direct mechanical and electrical compatibility with standard TO-92 through-hole PCB layouts. Verify lead spacing and bend radius specifications with your PCB design if custom lead forming is required.

Q: What is the significance of the lower 30 MHz transition frequency in ZTX657STZ?

A: ZTX657STZ provides 30 MHz transition frequency compared to 50 MHz in KSP42BU and 75 MHz in ZTX457. This parameter indicates the frequency at which transistor current gain begins to decrease. For applications operating below 30 MHz, ZTX657STZ provides adequate performance. For applications requiring operation at or above 30 MHz, ZTX457 or the baseline KSP42BU / MPSA42 parts are more appropriate.

Q: How do DC current gain specifications differ across substitute parts?

A: KSP42BU, MPSA42, and MPSA42BK specify minimum DC current gain (hFE) of 40 at 30 mA collector current and 10 V collector-emitter voltage. ZTX457 specifies minimum hFE of 50 at 50 mA and 10 V. ZTX657STZ specifies minimum hFE of 50 at 100 mA and 5 V. These variations reflect different transistor design characteristics. Verify that the specified gain at your operating point meets circuit requirements.

Q: What compliance certifications should I verify for my application?

A: KSP42BU is ROHS3 compliant and REACH Unaffected. MPSA42 and MPSA42BK show RoHS status as Not applicable and REACH status as Vendor Undefined. ZTX457 and ZTX657STZ are both ROHS3 compliant and REACH Unaffected. If your application requires specific compliance certifications, select parts with matching status or obtain compliance documentation from the manufacturer.

Q: Can I use ZTX657STZ in a design optimized for 50 MHz operation?

A: ZTX657STZ provides 30 MHz transition frequency, which is lower than the design baseline of 50 MHz. While the part may function in the circuit, it does not provide the same frequency performance margin. For applications requiring 50 MHz or higher operation, use KSP42BU, MPSA42, MPSA42BK, or ZTX457 instead.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message