FSB649 Equivalent & Substitute Parts

Part Overview

The FSB649 is an NPN Bipolar Junction Transistor (BJT) manufactured by onsemi, designed for surface mount applications in the SOT-23-3 package. This transistor operates at a maximum collector current of 3 A, collector-emitter breakdown voltage of 25 V, and maximum power dissipation of 500 mW. The device is rated for transition frequency of 150 MHz and operates across a temperature range of -55°C to 150°C. The FSB649 maintains Active product status and is ROHS3 compliant with unlimited moisture sensitivity level (MSL 1). Equivalent and substitute parts are identified to provide design flexibility for applications requiring comparable electrical and mechanical characteristics, particularly when the primary part is unavailable or when design specifications permit operation within the parameter ranges of alternative devices.

Key Parameters

Parameter	FSB649 Value	Unit
Transistor Type	NPN	—
Current - Collector (Ic) (Max)	3	A
Voltage - Collector Emitter Breakdown (Max)	25	V
Vce Saturation (Max) @ Ib, Ic	600 mV @ 300 mA, 3 A	—
Power - Max	500	mW
Frequency - Transition	150	MHz
Operating Temperature Range	-55 to 150	°C
Package / Case	SOT-23-3 (TO-236-3, SC-59)	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the FSB649 is determined by electrical and mechanical compatibility across the following critical parameters:

Electrical Compatibility Criteria:

Transistor Type: All substitutes must be NPN configuration
Collector-Emitter Breakdown Voltage (Vceo): Substitute voltage rating must equal or exceed the FSB649 rating of 25 V
Maximum Collector Current (Ic): Substitute current rating must equal or exceed the FSB649 rating of 3 A
Power Dissipation (Pmax): Substitute power rating must equal or exceed the FSB649 rating of 500 mW
Transition Frequency (fT): Substitute frequency must equal or exceed the FSB649 rating of 150 MHz
Operating Temperature Range: Substitute must support the FSB649 range of -55°C to 150°C

Mechanical Compatibility Criteria:

Package Type: All substitutes must use SOT-23-3 (TO-236-3, SC-59) surface mount package
Mounting Type: All substitutes must be surface mount compatible
Compliance: All substitutes must maintain ROHS3 compliance and MSL 1 rating

Substitution Logic: Substitutes are grouped based on whether they meet or exceed all electrical parameters while maintaining identical package and mounting specifications. Parts that fall below any critical electrical parameter are classified as partial substitutes with application-dependent limitations.

Parameter Comparison

Parameter	FSB649	BC818-40LT1G	NSS20201LT1G	2SC3265-Y,LF	PBSS4230T,215
Manufacturer	onsemi	onsemi	onsemi	Toshiba Semiconductor and Storage	Nexperia USA Inc.
Transistor Type	NPN	NPN	NPN	NPN	NPN
Current - Collector (Ic) (Max)	3 A	500 mA	2 A	800 mA	2 A
Voltage - Collector Emitter Breakdown (Max)	25 V	25 V	20 V	25 V	30 V
Power - Max	500 mW	225 mW	460 mW	200 mW	480 mW
Frequency - Transition	150 MHz	100 MHz	150 MHz	120 MHz	230 MHz
Operating Temperature Range	-55 to 150°C	-55 to 150°C	-55 to 150°C	to 150°C	to 150°C
Package / Case	SOT-23-3	SOT-23-3 (TO-236)	SOT-23-3 (TO-236)	TO-236-3	TO-236AB
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)
Product Status	Active	Active	Active	Active	Active

Engineering Selection Recommendations

Full Electrical Equivalents: No substitute part listed meets or exceeds all electrical parameters of the FSB649. The FSB649 specifies a maximum collector current of 3 A, which is the highest rating among all listed alternatives.

Partial Substitutes with Parameter Derating:

NSS20201LT1G operates at 2 A maximum collector current and 460 mW power dissipation, falling below the FSB649 specifications for current and power. This part is suitable for applications where the design current requirement does not exceed 2 A and power dissipation remains below 460 mW. The NSS20201LT1G maintains identical transition frequency (150 MHz) and operating temperature range (-55°C to 150°C) as the FSB649. Voltage rating of 20 V is below the FSB649 specification of 25 V.

PBSS4230T,215 operates at 2 A maximum collector current and 480 mW power dissipation, also below FSB649 specifications for current and power. This part provides a higher voltage rating of 30 V and superior transition frequency of 230 MHz. The PBSS4230T,215 carries automotive qualification (AEC-Q100) and is suitable for applications where the design current requirement does not exceed 2 A. Operating temperature range is specified to 150°C maximum.

BC818-40LT1G operates at 500 mA maximum collector current and 225 mW power dissipation, representing the most significant derating from FSB649 specifications. This part is suitable only for low-current applications not exceeding 500 mA. Transition frequency is 100 MHz, below the FSB649 specification of 150 MHz.

2SC3265-Y,LF operates at 800 mA maximum collector current and 200 mW power dissipation, below FSB649 specifications for current and power. This part is suitable for applications where the design current requirement does not exceed 800 mA. Transition frequency is 120 MHz, below the FSB649 specification of 150 MHz.

All substitute parts maintain ROHS3 compliance, MSL 1 rating, and Active product status. All parts are packaged in SOT-23-3 (TO-236) surface mount configuration with identical pin compatibility.

Frequently Asked Questions (FAQ)

Q: Can the BC818-40LT1G directly replace the FSB649 in all applications?

A: No. The BC818-40LT1G is rated for a maximum collector current of 500 mA, while the FSB649 is rated for 3 A. Direct substitution is limited to applications where the design current does not exceed 500 mA. Additionally, the BC818-40LT1G transition frequency is 100 MHz compared to the FSB649 specification of 150 MHz.

Q: What is the primary limitation of the NSS20201LT1G as a substitute for the FSB649?

A: The NSS20201LT1G is limited by maximum collector current of 2 A and maximum power dissipation of 460 mW, both below the FSB649 specifications of 3 A and 500 mW respectively. The NSS20201LT1G collector-emitter breakdown voltage is 20 V, below the FSB649 specification of 25 V. Substitution is appropriate only when the application design current does not exceed 2 A and voltage stress remains below 20 V.

Q: Are all substitute parts compatible with the same PCB footprint as the FSB649?

A: Yes. All listed substitute parts use the SOT-23-3 (TO-236-3, SC-59) surface mount package, which provides identical pin configuration and PCB footprint compatibility with the FSB649. No PCB layout modifications are required for mechanical substitution.

Q: Does the PBSS4230T,215 offer any advantages over the FSB649?

A: The PBSS4230T,215 provides a higher collector-emitter breakdown voltage rating of 30 V compared to the FSB649 specification of 25 V, and a superior transition frequency of 230 MHz compared to 150 MHz. The PBSS4230T,215 carries automotive qualification (AEC-Q100). However, the PBSS4230T,215 is limited to 2 A maximum collector current and 480 mW power dissipation, below the FSB649 specifications.

Q: What compliance certifications are maintained across all substitute parts?

A: All substitute parts maintain ROHS3 compliance and Moisture Sensitivity Level 1 (Unlimited). All parts carry Active product status. The PBSS4230T,215 additionally carries AEC-Q100 automotive qualification.

Q: Can the 2SC3265-Y,LF be used in high-frequency applications requiring 150 MHz operation?

A: The 2SC3265-Y,LF is rated for transition frequency of 120 MHz, which is below the FSB649 specification of 150 MHz. Use of the 2SC3265-Y,LF in applications requiring 150 MHz operation is not supported by the specified electrical parameters.

Q: What is the collector current derating for each substitute part relative to the FSB649?

A: BC818-40LT1G: 83% derating (500 mA vs. 3 A). NSS20201LT1G: 33% derating (2 A vs. 3 A). 2SC3265-Y,LF: 73% derating (800 mA vs. 3 A). PBSS4230T,215: 33% derating (2 A vs. 3 A).

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