KSP43BU Equivalent & Substitute Parts

Part Overview

The KSP43BU is an NPN bipolar junction transistor manufactured by onsemi, designed for small-signal switching and amplification applications. This device features a 200 V collector-emitter breakdown voltage rating, 500 mA maximum collector current, and 625 mW power dissipation capability in a TO-92-3 through-hole package. The KSP43BU is classified as Last Time Buy, indicating that onsemi has discontinued this part number. Identifying equivalent and substitute parts is necessary to ensure design continuity and maintain supply chain reliability for existing applications and new designs requiring comparable performance characteristics.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Current - Collector (Ic) Max	500	mA
Voltage - Collector Emitter Breakdown (Max)	200	V
Vce Saturation (Max)	500 mV @ 2 mA, 20 mA	—
Current - Collector Cutoff (Max)	100	nA
DC Current Gain (hFE) Min	40 @ 30 mA, 10 V	—
Power - Max	625	mW
Frequency - Transition	50	MHz
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
Package / Case	TO-92-3	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitute parts for the KSP43BU are identified based on electrical and mechanical compatibility within the NPN bipolar junction transistor category. The substitution logic is based on the following critical parameters:

Electrical Compatibility Criteria:

Transistor type must be NPN
Collector current rating must equal or exceed 500 mA
Collector-emitter breakdown voltage must equal or exceed 200 V
DC current gain (hFE) characteristics must support the intended application bias point
Vce saturation characteristics must be compatible with switching or linear operation requirements
Power dissipation capability must support the thermal requirements of the application

Mechanical Compatibility Criteria:

Through-hole mounting type
Package footprint compatibility (TO-92-3 or TO-92 compatible packages)

Compliance Criteria:

RoHS3 compliance required
REACH unaffected status

The KSP43BU from onsemi and the KSP43BU from Fairchild Semiconductor are parametric equivalents, sharing identical electrical specifications and package designation. The ZTX696B from Diodes Incorporated is a functional substitute with comparable electrical performance and enhanced specifications in certain parameters.

Parameter Comparison

Parameter	KSP43BU (onsemi)	KSP43BU (Fairchild)	ZTX696B (Diodes)
Manufacturer	onsemi	Fairchild Semiconductor	Diodes Incorporated
Transistor Type	NPN	NPN	NPN
Current - Collector (Ic) Max	500 mA	500 mA	500 mA
Voltage - Collector Emitter Breakdown (Max)	200 V	200 V	180 V
Vce Saturation (Max)	500 mV @ 2 mA, 20 mA	500 mV @ 2 mA, 20 mA	250 mV @ 5 mA, 200 mA
Current - Collector Cutoff (Max)	100 nA	100 nA	100 nA
DC Current Gain (hFE) Min	40 @ 30 mA, 10 V	40 @ 30 mA, 10 V	150 @ 200 mA, 5 V
Power - Max	625 mW	625 mW	1 W
Frequency - Transition	50 MHz	50 MHz	70 MHz
Operating Temperature (TJ)	150°C	150°C	−55°C to 200°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	TO-92-3	TO-92-3	E-Line (TO-92 compatible)
Product Status	Last Time Buy	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

KSP43BU (Fairchild Semiconductor): This part is the primary parametric equivalent to the onsemi KSP43BU. It maintains identical electrical specifications, package designation, and compliance certifications. The Fairchild variant is classified as Active product status, ensuring continued availability and supply chain stability. This part is the direct replacement for applications currently using the onsemi KSP43BU and should be the first selection for new designs requiring KSP43BU-level performance.

ZTX696B (Diodes Incorporated): This part functions as a substitute for applications where the KSP43BU specifications can be accommodated within a design margin. The ZTX696B offers enhanced performance in several parameters: higher power dissipation (1 W versus 625 mW), higher transition frequency (70 MHz versus 50 MHz), and superior DC current gain (150 @ 200 mA, 5 V). However, the collector-emitter breakdown voltage is reduced to 180 V, which is acceptable only for applications with maximum operating voltages below 180 V. The ZTX696B features an extended operating temperature range (−55°C to 200°C) and improved Vce saturation characteristics (250 mV versus 500 mV). The E-Line package is mechanically compatible with TO-92-3 footprints. The ZTX696B is classified as Active product status with higher inventory availability.

Both substitute parts maintain RoHS3 compliance and REACH unaffected status, ensuring regulatory alignment with the original KSP43BU specification.

Frequently Asked Questions (FAQ)

Q: Can the Fairchild KSP43BU be used as a direct replacement for the onsemi KSP43BU?

A: Yes. The Fairchild KSP43BU is a parametric equivalent with identical electrical specifications, including collector current (500 mA), collector-emitter breakdown voltage (200 V), power dissipation (625 mW), transition frequency (50 MHz), and DC current gain (40 @ 30 mA, 10 V). Both parts use the TO-92-3 package and maintain ROHS3 compliance. No circuit modifications are required.

Q: Under what conditions can the ZTX696B substitute for the KSP43BU?

A: The ZTX696B can substitute for the KSP43BU in applications where the maximum operating voltage does not exceed 180 V. The ZTX696B meets or exceeds all other critical parameters: collector current (500 mA), power dissipation (1 W), transition frequency (70 MHz), and DC current gain (150 @ 200 mA, 5 V). The ZTX696B offers superior saturation characteristics (250 mV versus 500 mV) and an extended operating temperature range. The E-Line package is mechanically compatible with TO-92-3 footprints.

Q: What is the difference between the TO-92-3 and E-Line packages?

A: Both packages are through-hole, three-lead configurations designed for small-signal transistors. The TO-92-3 (TO-226AA) is the standard package for the KSP43BU. The E-Line is a compatible variant used by Diodes Incorporated for the ZTX696B. Both packages share the same pin spacing and footprint compatibility, allowing direct substitution on printed circuit boards designed for TO-92-3 components.

Q: Why is the onsemi KSP43BU classified as Last Time Buy?

A: Last Time Buy status indicates that onsemi has discontinued the KSP43BU and will no longer manufacture this part after existing inventory is depleted. This classification necessitates identifying equivalent parts from other manufacturers to ensure long-term design support and supply chain continuity.

Q: Are there any compliance differences between the three parts?

A: All three parts (onsemi KSP43BU, Fairchild KSP43BU, and ZTX696B) are ROHS3 compliant and REACH unaffected. No compliance barriers exist for substitution between these parts.

Q: What is the significance of the DC current gain (hFE) difference between the KSP43BU and ZTX696B?

A: The KSP43BU specifies a minimum hFE of 40 @ 30 mA, 10 V, while the ZTX696B specifies 150 @ 200 mA, 5 V. These specifications are measured at different bias points and reflect different transistor characteristics. The ZTX696B exhibits higher current gain at higher collector currents, which may improve switching speed and reduce base drive requirements in certain circuit topologies. Circuit verification is necessary to confirm compatibility with existing bias networks.

Q: Can the KSP43BU be used in high-temperature applications?

A: The KSP43BU is rated for a maximum junction temperature of 150°C. Applications requiring operation above 150°C should use the ZTX696B, which is rated to 200°C maximum junction temperature. The extended temperature range of the ZTX696B provides additional thermal margin for high-temperature environments.

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