KSC1623LMTF Equivalent & Substitute Parts

Part Overview

The KSC1623LMTF is an NPN bipolar junction transistor manufactured by onsemi, housed in a SOT-23-3 surface mount package. This device is rated for 50 V collector-emitter breakdown voltage with a maximum collector current of 100 mA and 200 mW power dissipation. The transistor operates at a transition frequency of 250 MHz with a maximum junction temperature of 150°C.

The KSC1623LMTF is classified as obsolete. Substitute components are necessary to maintain design continuity and ensure availability for new production runs, repairs, and system upgrades. Equivalent parts must maintain functional compatibility across critical electrical parameters while conforming to the same physical package specification.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	50	V
Current - Collector (Ic) (Max)	100	mA
Power - Max	200	mW
Frequency - Transition	250	MHz
Package / Case	SOT-23-3	—
Mounting Type	Surface Mount	—
Operating Temperature (Max)	150	°C
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the KSC1623LMTF is determined by the following critical parameters:

Package Compatibility: All substitute parts must use the SOT-23-3 (TO-236-3, SC-59) surface mount package to ensure mechanical and electrical compatibility with existing PCB layouts.

Transistor Type: All substitutes must be NPN-type bipolar junction transistors to maintain circuit polarity and biasing requirements.

Voltage Rating: Substitute parts must have a collector-emitter breakdown voltage (VCEO) equal to or greater than 50 V. Parts rated at 45 V do not meet the minimum voltage requirement of the original specification and are not suitable for direct substitution in applications requiring the full 50 V rating. Parts rated at 60 V or higher provide adequate voltage margin.

Current Rating: Substitute parts must support a maximum collector current (Ic) of at least 100 mA. Parts with higher current ratings (such as 500 mA) are acceptable as they provide additional design margin.

Power Dissipation: Substitute parts must have a maximum power rating of at least 200 mW. Parts rated at 225 mW or 300 mW are acceptable.

Frequency Response: The transition frequency (fT) of 250 MHz in the original part is a performance specification. Substitute parts with lower transition frequencies (100 MHz) will have reduced high-frequency performance characteristics.

Product Status and Compliance: Active product status ensures ongoing availability and support. All substitute parts must maintain ROHS3 compliance and MSL Level 1 (Unlimited) moisture sensitivity rating to match the original specification.

Parameter Comparison

Part Number	Manufacturer	Ic (Max) mA	VCEO (Max) V	Power (Max) mW	fT MHz	Package	Product Status	RoHS
KSC1623LMTF	onsemi	100	50	200	250	SOT-23-3	Obsolete	ROHS3
BC817-40LT1G	onsemi	500	45	300	100	SOT-23-3	Active	ROHS3
BC847ALT1G	onsemi	100	45	300	100	SOT-23-3	Active	ROHS3
BC847BLT1G	onsemi	100	45	300	100	SOT-23-3	Active	ROHS3
BC847BLT3G	onsemi	100	45	300	100	SOT-23-3	Active	ROHS3
BC847CLT1G	onsemi	100	45	300	100	SOT-23-3	Active	ROHS3
BC847CLT3G	onsemi	100	45	300	100	SOT-23-3	Active	ROHS3
BC850BLT1G	onsemi	100	45	225	100	SOT-23-3	Active	ROHS3
BC850CLT1G	onsemi	100	45	225	100	SOT-23-3	Active	ROHS3
BCW72LT1G	onsemi	100	45	300	300	SOT-23-3	Active	ROHS3
MMBT2484LT1G	onsemi	100	60	225	—	SOT-23-3	Active	ROHS3

Engineering Selection Recommendations

Voltage Compatibility Constraint: The KSC1623LMTF specifies a 50 V collector-emitter breakdown voltage. Substitute parts with 45 V ratings (BC817-40LT1G, BC847ALT1G, BC847BLT1G, BC847BLT3G, BC847CLT1G, BC847CLT3G, BC850BLT1G, BC850CLT1G, and BCW72LT1G) do not meet the minimum voltage specification and are not suitable for direct substitution in applications requiring the full 50 V operating margin.

Acceptable Substitute: MMBT2484LT1G is the only substitute part that meets or exceeds the 50 V voltage requirement with a 60 V collector-emitter breakdown rating. This part maintains the 100 mA collector current specification, provides adequate power dissipation at 225 mW, and is housed in the identical SOT-23-3 package. The MMBT2484LT1G carries active product status with ROHS3 compliance and MSL Level 1 rating, ensuring long-term availability and regulatory conformance.

Product Status: All substitute parts listed carry active product status, ensuring continued manufacturing support and supply chain availability. The KSC1623LMTF obsolete status necessitates transition to an active equivalent for new designs and ongoing production.

Regulatory Compliance: All substitute parts maintain ROHS3 compliance and unlimited moisture sensitivity level (MSL 1), matching the environmental and regulatory requirements of the original component.

Frequently Asked Questions (FAQ)

Q: Can BC847 series transistors substitute for the KSC1623LMTF?

A: BC847 series transistors (BC847ALT1G, BC847BLT1G, BC847BLT3G, BC847CLT1G, BC847CLT3G) are not suitable direct substitutes. These parts are rated at 45 V collector-emitter breakdown voltage, which falls below the 50 V specification of the KSC1623LMTF. Applications requiring the full 50 V operating margin will not be adequately protected with these lower-rated devices.

Q: What is the difference between BC847A, BC847B, and BC847C variants?

A: The BC847 variants differ in their DC current gain (hFE) specifications. BC847A has a minimum hFE of 110 at specified test conditions, BC847B has 200, and BC847C has 420. All three variants share identical voltage, current, and package specifications. Selection between variants depends on the specific gain requirements of the application circuit.

Q: Is the MMBT2484LT1G a direct replacement for the KSC1623LMTF?

A: The MMBT2484LT1G meets the critical electrical requirements for substitution: it maintains the SOT-23-3 package, supports 100 mA collector current, and exceeds the 50 V voltage requirement with a 60 V rating. The 225 mW power rating is lower than the original 200 mW specification but remains adequate for the same current and voltage operating conditions. The transition frequency specification is not provided for the MMBT2484LT1G, which may affect high-frequency performance in applications sensitive to fT characteristics.

Q: Why do some substitute parts have higher current ratings (500 mA)?

A: The BC817-40LT1G is rated for 500 mA maximum collector current, compared to 100 mA for the KSC1623LMTF. Higher current ratings provide additional design margin and allow the device to operate in applications with greater current demands. However, this part does not meet the 50 V voltage requirement and is not suitable as a direct substitute.

Q: What is the significance of the SOT-23-3 package specification?

A: The SOT-23-3 package (also designated TO-236-3 or SC-59) is a three-terminal surface mount package with standardized pin configuration and footprint. All substitute parts must use this identical package to ensure mechanical compatibility with existing PCB layouts, solder reflow processes, and automated assembly equipment.

Q: Are there differences in packaging options among the substitute parts?

A: Substitute parts are supplied in different packaging formats: Cut Tape (CT) & Digi-Reel®, Tape & Reel (TR), or other configurations. These packaging options do not affect electrical performance or PCB compatibility. Selection of packaging format depends on production volume requirements and inventory management practices.

Q: How does transition frequency (fT) affect circuit performance?

A: Transition frequency represents the frequency at which the transistor's current gain drops to unity. The KSC1623LMTF operates at 250 MHz, while most BC847 and BC850 substitutes operate at 100 MHz. BCW72LT1G operates at 300 MHz. Applications requiring high-frequency switching or amplification performance may be affected by lower transition frequency ratings. MMBT2484LT1G does not specify transition frequency.

Q: What does ROHS3 compliance mean?

A: ROHS3 compliance indicates conformance to the Restriction of Hazardous Substances Directive 3, which restricts the use of specific hazardous materials including lead, cadmium, mercury, and certain flame retardants in electrical and electronic equipment. All listed substitute parts maintain ROHS3 compliance, ensuring regulatory conformance for applications subject to environmental restrictions.

Q: What is MSL Level 1 moisture sensitivity?

A: MSL (Moisture Sensitivity Level) 1 indicates unlimited shelf life without moisture control requirements. Components at this level do not require special drying or moisture-barrier packaging. All listed parts maintain MSL Level 1 rating, matching the original KSC1623LMTF specification and eliminating special handling requirements during storage and assembly.

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