KSC945YBU Equivalent & Substitute Parts

Part Overview

The KSC945YBU is an NPN bipolar junction transistor manufactured by onsemi, rated for 50V collector-emitter breakdown voltage and 150mA maximum collector current. This device is packaged in a TO-92-3 through-hole configuration and is designated as Last Time Buy status. The KSC945YBU serves general-purpose switching and amplification applications in consumer and industrial electronics. Due to its Last Time Buy status, identifying equivalent and substitute parts is necessary for design continuity and long-term supply chain planning.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	50	V
Current - Collector (Ic) (Max)	150	mA
Power - Max	250	mW
Frequency - Transition	300	MHz
Vce Saturation (Max) @ Ib, Ic	300mV @ 10mA, 100mA	—
DC Current Gain (hFE) (Min) @ Ic, Vce	120 @ 1mA, 6V	—
Mounting Type	Through Hole	—
Package / Case	TO-92-3	—
Operating Temperature (Max)	150	°C
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the KSC945YBU is determined by the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

Transistor type must be NPN
Voltage - Collector Emitter Breakdown (Max) must be ≥50V
Current - Collector (Ic) (Max) must be ≥150mA
Power dissipation (Max) must be ≥250mW
Frequency - Transition must support the application frequency requirements
Vce Saturation characteristics must be compatible with circuit switching requirements
DC Current Gain (hFE) must meet or exceed minimum specifications

Mechanical Compatibility Criteria:

Mounting type must be Through Hole
Package must be TO-92-3 or equivalent TO-226-3 footprint
Pin configuration must be compatible with existing PCB layouts

Compliance Requirements:

RoHS3 compliance required
REACH Unaffected status required

Substitute parts are grouped based on whether they meet all electrical parameters while maintaining mechanical and package compatibility.

Parameter Comparison

Parameter	KSC945YBU (onsemi)	2N6428 PBFREE (Central Semiconductor)	KSC945YBU (Fairchild Semiconductor)
Transistor Type	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	50V	50V	50V
Current - Collector (Ic) (Max)	150mA	200mA	150mA
Power - Max	250mW	1.5W	250mW
Frequency - Transition	300MHz	100MHz	300MHz
Vce Saturation (Max) @ Ib, Ic	300mV @ 10mA, 100mA	600mV @ 5mA, 100mA	300mV @ 10mA, 100mA
DC Current Gain (hFE) (Min) @ Ic, Vce	120 @ 1mA, 6V	250 @ 10mA, 5V	120 @ 1mA, 6V
Operating Temperature (Max)	150°C	150°C	150°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	TO-92-3	TO-92-3	TO-92-3
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Not specified
Product Status	Last Time Buy	Active	Active

Engineering Selection Recommendations

KSC945YBU (Fairchild Semiconductor) is a parametric equivalent to the onsemi KSC945YBU. Both devices share identical electrical specifications including 50V breakdown voltage, 150mA maximum collector current, 250mW power rating, and 300MHz transition frequency. Both are packaged in TO-92-3 through-hole configuration. The Fairchild variant is in Active product status, providing supply continuity for the Last Time Buy onsemi part. RoHS3 compliance is confirmed for the onsemi version; compliance status for the Fairchild variant is not specified in the provided data.

2N6428 PBFREE (Central Semiconductor) is a functional substitute with extended electrical capabilities. This device exceeds the KSC945YBU in maximum collector current (200mA vs. 150mA) and power dissipation (1.5W vs. 250mW), making it suitable for applications requiring higher current handling. However, the 2N6428 PBFREE operates at a lower transition frequency (100MHz vs. 300MHz) and exhibits higher Vce saturation voltage (600mV vs. 300mV). The 2N6428 PBFREE is in Active product status and is ROHS3 compliant. This substitute is appropriate for low-frequency switching applications where the reduced transition frequency does not impact circuit performance.

Selection between these substitutes depends on application frequency requirements and current/power demands. For direct replacement in existing designs, the Fairchild KSC945YBU is preferred. For applications with lower frequency requirements and higher current demands, the 2N6428 PBFREE is suitable.

Frequently Asked Questions (FAQ)

Q: Can the 2N6428 PBFREE directly replace the KSC945YBU in all applications?

A: The 2N6428 PBFREE is not a direct replacement for all applications. While both devices share the same 50V breakdown voltage and TO-92-3 package, the 2N6428 PBFREE has a transition frequency of 100MHz compared to the KSC945YBU's 300MHz. Applications operating above 100MHz require the KSC945YBU or the Fairchild equivalent. Additionally, the 2N6428 PBFREE exhibits higher Vce saturation voltage (600mV vs. 300mV), which affects switching speed and power dissipation in saturation mode.

Q: Is the Fairchild KSC945YBU a true equivalent to the onsemi KSC945YBU?

A: Yes. The Fairchild KSC945YBU is a parametric equivalent with identical electrical specifications: 50V breakdown voltage, 150mA maximum collector current, 250mW power rating, 300MHz transition frequency, and matching Vce saturation and DC current gain characteristics. Both devices use the TO-92-3 through-hole package. The primary difference is manufacturer and product status (Fairchild is Active vs. onsemi is Last Time Buy).

Q: What is the significance of the TO-92-3 package specification?

A: The TO-92-3 package is a three-lead through-hole configuration with a specific pin layout and footprint. All listed substitutes use this package, ensuring mechanical and electrical compatibility with existing PCB designs. The TO-92-3 designation is equivalent to TO-226-3 and TO-226AA specifications.

Q: Are all listed parts RoHS3 compliant?

A: The onsemi KSC945YBU and 2N6428 PBFREE are confirmed ROHS3 compliant. RoHS3 compliance status for the Fairchild KSC945YBU is not specified in the provided data.

Q: What does "Last Time Buy" status mean for the onsemi KSC945YBU?

A: Last Time Buy status indicates that onsemi will discontinue production of this part. Existing inventory is available for purchase, but no future production is planned. This status necessitates identifying and qualifying substitute parts for long-term design continuity.

Q: How do the DC Current Gain (hFE) specifications differ between substitutes?

A: The onsemi and Fairchild KSC945YBU specify hFE (Min) of 120 @ 1mA, 6V. The 2N6428 PBFREE specifies hFE (Min) of 250 @ 10mA, 5V. These measurements are taken at different operating points, making direct comparison difficult. The higher hFE value of the 2N6428 PBFREE indicates greater current amplification capability at its specified test conditions.

Q: Can the KSC945YBU be used in high-frequency applications above 300MHz?

A: The KSC945YBU has a transition frequency of 300MHz, which defines the frequency at which current gain begins to degrade significantly. Applications requiring operation above 300MHz require devices with higher transition frequency specifications. The 2N6428 PBFREE, with 100MHz transition frequency, is unsuitable for frequencies above 100MHz.

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