2STF1340 Equivalent & Substitute Parts

Part Overview

The 2STF1340 is an NPN bipolar junction transistor (BJT) manufactured by STMicroelectronics, designed for surface mount applications in the SOT-89-3 package. This component is rated for 40 V collector-emitter breakdown voltage with a maximum collector current of 3 A and 1.4 W power dissipation. The device operates at a transition frequency of 100 MHz with a maximum junction temperature of 150°C.

The 2STF1340 is classified as obsolete. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for applications utilizing this transistor specification.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	40	V
Current - Collector (Ic) (Max)	3	A
Power - Max	1.4	W
Frequency - Transition	100	MHz
Package / Case	TO-243AA (SOT-89-3)	—
Mounting Type	Surface Mount	—
Operating Temperature (Max)	150	°C
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitute parts for the 2STF1340 are selected based on electrical and mechanical compatibility within the following criteria:

Primary Compatibility Parameters:

Transistor Type: NPN
Package / Case: TO-243AA (SOT-89-3)
Mounting Type: Surface Mount
Voltage - Collector Emitter Breakdown: 40 V or higher
Current - Collector (Ic) (Max): Equal to or greater than 3 A
Power - Max: Equal to or greater than 1.4 W
Operating Temperature: Maximum 150°C or higher
RoHS Status: ROHS3 Compliant

Substitute parts are grouped into two categories:

Category 1: Direct Electrical Equivalents Parts meeting or exceeding all primary electrical parameters (40 V, 3 A, 1.4 W minimum) with identical package specifications.

Category 2: Functional Alternatives Parts with lower current or power ratings suitable for applications where the full 3 A specification is not required, maintaining voltage and package compatibility.

Parameter Comparison

Part Number	Manufacturer	Ic (Max)	Vce Breakdown (Max)	Power (Max)	Frequency	Product Status	Inventory
2STF1340	STMicroelectronics	3 A	40 V	1.4 W	100 MHz	Obsolete	7154 Pcs
FCX1051ATA	Diodes Incorporated	3 A	40 V	1 W	155 MHz	Active	2351 Pcs
DSS4540X-13	Diodes Incorporated	4 A	40 V	900 mW	70 MHz	Active	15205 Pcs
FCX690BTA	Diodes Incorporated	2 A	45 V	2 W	150 MHz	Active	29300 Pcs
FCX491ATA	Diodes Incorporated	1 A	40 V	1 W	150 MHz	Active	19556 Pcs
BCX54TA	Diodes Incorporated	1 A	45 V	1 W	150 MHz	Active	8100 Pcs
DXT2222A-13	Diodes Incorporated	600 mA	40 V	1 W	300 MHz	Active	6361 Pcs
DXT3904-13	Diodes Incorporated	200 mA	40 V	1 W	300 MHz	Active	77700 Pcs

Engineering Selection Recommendations

Primary Recommendation: FCX1051ATA

The FCX1051ATA is the closest electrical equivalent to the 2STF1340. It provides identical collector current (3 A) and collector-emitter breakdown voltage (40 V) specifications. The FCX1051ATA is manufactured by Diodes Incorporated with active product status, ensuring long-term availability. This part is ROHS3 compliant and carries the same MSL rating (1 - Unlimited). The higher transition frequency (155 MHz versus 100 MHz) provides additional performance margin. Inventory availability is 2351 pieces.

Secondary Recommendation: DSS4540X-13

The DSS4540X-13 exceeds the collector current specification at 4 A while maintaining the 40 V voltage rating. This part offers superior current handling capability and is suitable for applications requiring higher current margins. The DSS4540X-13 is active with 15205 pieces in inventory. The lower transition frequency (70 MHz) is acceptable for applications not requiring the full 100 MHz bandwidth. ROHS3 compliance and MSL rating are equivalent to the main part.

Alternative for Lower Current Applications: FCX491ATA or BCX54TA

For applications where the full 3 A specification is not required, the FCX491ATA (1 A) or BCX54TA (1 A) provide active alternatives with higher transition frequencies (150 MHz). Both parts maintain 40 V or higher voltage ratings and are ROHS3 compliant. These options are suitable for signal-level switching and low-power amplification circuits.

Alternative for Power-Constrained Applications: FCX690BTA

The FCX690BTA provides 2 A collector current with 2 W power dissipation, exceeding the 1.4 W rating of the 2STF1340. This part is suitable for applications requiring higher power handling with moderate current levels. The 45 V voltage rating provides additional voltage margin. Inventory availability is 29300 pieces.

All recommended substitutes are ROHS3 compliant, carry MSL rating 1 (Unlimited), and are packaged in the identical TO-243AA (SOT-89-3) surface mount configuration.

Frequently Asked Questions (FAQ)

Q: Can the FCX1051ATA directly replace the 2STF1340 in all applications?

A: The FCX1051ATA is electrically compatible with the 2STF1340 for applications requiring 3 A collector current at 40 V. Both parts share identical current and voltage ratings, the same package (SOT-89-3), and equivalent thermal specifications. The higher transition frequency of the FCX1051ATA (155 MHz versus 100 MHz) is not detrimental to applications designed for 100 MHz operation. Verification of DC current gain (hFE) characteristics may be necessary for precision amplifier circuits, as the FCX1051ATA specifies 290 @ 10mA, 2V compared to 180 @ 1A, 2V for the 2STF1340.

Q: What is the difference between the DSS4540X-13 and FCX1051ATA?

A: Both parts maintain 40 V voltage rating and are suitable for the 2STF1340 application space. The DSS4540X-13 provides higher collector current (4 A versus 3 A) but operates at a lower transition frequency (70 MHz versus 155 MHz). The DSS4540X-13 is appropriate for high-current switching applications where frequency response below 100 MHz is acceptable. The FCX1051ATA is preferred for applications requiring the specified 100 MHz or higher frequency performance.

Q: Are all substitute parts available in the same packaging?

A: Yes. All substitute parts listed are packaged in TO-243AA (SOT-89-3) surface mount configuration, identical to the 2STF1340. This ensures mechanical and thermal compatibility with existing PCB layouts and assembly processes. All parts carry MSL rating 1 (Unlimited), indicating no moisture sensitivity restrictions.

Q: What is the significance of the transition frequency difference between parts?

A: Transition frequency (fT) indicates the frequency at which the transistor's current gain drops to unity. The 2STF1340 specifies 100 MHz. Substitute parts with higher transition frequencies (such as FCX1051ATA at 155 MHz or DXT2222A-13 at 300 MHz) provide additional frequency margin and are suitable for applications designed for the 100 MHz specification. Parts with lower transition frequencies (such as DSS4540X-13 at 70 MHz) are suitable only for applications where the operating frequency does not exceed the specified fT.

Q: How do I select between multiple substitute options?

A: Selection depends on application requirements. For direct replacement with maximum compatibility, select FCX1051ATA (identical 3 A, 40 V ratings). For applications requiring higher current capability, select DSS4540X-13 (4 A). For lower-current applications (under 1 A), select FCX491ATA or BCX54TA. For applications requiring higher power dissipation, select FCX690BTA (2 W). All selections must verify that the chosen part's electrical characteristics (particularly DC current gain and saturation voltage) are compatible with the circuit design.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed carry ROHS3 compliance certification, matching the environmental compliance status of the 2STF1340. All parts are also REACH unaffected and carry identical ECCN and HTSUS classifications.

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