KSE800S Equivalent & Substitute Parts

Part Overview

The KSE800S is an NPN Darlington bipolar junction transistor manufactured by onsemi, rated for 60 V collector-emitter breakdown voltage and 4 A maximum collector current in a TO-126-3 through-hole package. This device is classified as obsolete, necessitating identification of active equivalent and substitute components for ongoing design requirements and production continuity.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN - Darlington	—
Current - Collector (Ic) (Max)	4	A
Voltage - Collector Emitter Breakdown (Max)	60	V
Power - Max	40	W
DC Current Gain (hFE) (Min)	750	—
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
Package / Case	TO-225AA, TO-126-3	—

Substitute Part Grouping Explanation

Substitution of the KSE800S is determined by electrical and mechanical parameter equivalence within the NPN Darlington transistor category. The critical parameters governing substitution are:

Collector Current Rating (Ic): 4 A maximum
Collector-Emitter Breakdown Voltage (VCEO): 60 V maximum
Power Dissipation: 40 W maximum
DC Current Gain (hFE): Minimum 750 at specified operating conditions
Operating Temperature: 150°C junction temperature
Mounting Configuration: Through-hole technology
Package Compatibility: TO-126-3 or equivalent mechanical footprint

Parts meeting these electrical specifications and physical mounting requirements are classified as direct equivalents or functionally compatible substitutes. Variations in saturation voltage characteristics or cutoff current do not preclude substitution when primary electrical ratings remain within specified limits.

Parameter Comparison

Parameter	KSE800S (onsemi)	KSE800STU (Fairchild)	BD677 (STMicroelectronics)	BD677A (STMicroelectronics)
Transistor Type	NPN - Darlington	NPN - Darlington	NPN - Darlington	NPN - Darlington
Current - Collector (Ic) (Max)	4 A	4 A	4 A	4 A
Voltage - Collector Emitter Breakdown (Max)	60 V	60 V	60 V	60 V
Vce Saturation (Max) @ Ib, Ic	2.5V @ 30mA, 1.5A	2.5V @ 30mA, 1.5A	2.5V @ 30mA, 1.5A	2.8V @ 40mA, 2A
Current - Collector Cutoff (Max)	100µA	100µA	500µA	500µA
DC Current Gain (hFE) (Min) @ Ic, Vce	750 @ 1.5A, 3V	750 @ 1.5A, 3V	750 @ 1.5A, 3V	750 @ 2A, 3V
Power - Max	40 W	40 W	40 W	40 W
Operating Temperature (TJ)	150°C	150°C	150°C	150°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Supplier Device Package	TO-126-3	TO-126-3	SOT-32-3	SOT-32-3
Product Status	Obsolete	Active	Active	Active
RoHS Status	—	—	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	Vendor Undefined	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

KSE800STU (Fairchild Semiconductor) is the primary direct equivalent to the KSE800S. This part maintains identical electrical specifications and TO-126-3 package configuration. The KSE800STU carries active product status, ensuring continued availability and supply chain stability. This substitute is recommended for direct replacement in existing designs without modification.

BD677 (STMicroelectronics) provides electrical equivalence with identical primary ratings (4 A, 60 V, 40 W, 750 hFE minimum). The BD677 is supplied in SOT-32-3 package format, which differs mechanically from the TO-126-3 footprint. This part carries active product status and ROHS3 compliance certification. Physical board layout modification is required for implementation.

BD677A (STMicroelectronics) offers electrical compatibility with minor saturation voltage variation (2.8 V maximum at 40 mA, 2 A versus 2.5 V at 30 mA, 1.5 A). The BD677A is supplied in SOT-32-3 package format and carries active product status with ROHS3 compliance. Physical board layout modification is required for implementation.

Selection between substitute options depends on packaging constraints and design flexibility. The KSE800STU enables direct board-level replacement. The BD677 and BD677A require PCB layout adaptation but provide active product status and regulatory compliance certifications.

Frequently Asked Questions (FAQ)

Q: Can the KSE800STU replace the KSE800S without circuit modification?

A: Yes. The KSE800STU maintains identical electrical specifications and TO-126-3 package configuration. Direct substitution is possible without circuit redesign.

Q: What is the primary difference between BD677 and BD677A?

A: Both parts meet the 4 A, 60 V, 40 W electrical requirements. The BD677A exhibits higher saturation voltage (2.8 V maximum at 40 mA, 2 A) compared to the BD677 (2.5 V maximum at 30 mA, 1.5 A). Both are supplied in SOT-32-3 package format.

Q: Why do BD677 and BD677A require board layout modification?

A: The BD677 and BD677A are supplied in SOT-32-3 package format, which differs mechanically from the TO-126-3 footprint of the KSE800S. PCB land pattern and mounting hole configuration must be adapted for these substitutes.

Q: Are all substitute parts RoHS compliant?

A: The BD677 and BD677A carry ROHS3 compliance certification. The KSE800STU RoHS status is not specified in available documentation.

Q: What is the moisture sensitivity level for substitute parts?

A: The KSE800STU moisture sensitivity level is vendor undefined. The BD677 and BD677A both carry MSL 1 (Unlimited) classification, matching the original KSE800S specification.

Q: Can these parts be used interchangeably in high-frequency applications?

A: Transition frequency data is not provided for any of these parts. Selection for high-frequency applications requires additional frequency response characterization beyond the parameters specified.

Q: What inventory availability exists for these substitutes?

A: KSE800STU: 1798 pieces in stock. BD677: 1804 pieces in stock. BD677A: 2443 pieces in stock. The original KSE800S: 708 pieces in stock (obsolete status).

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