STN749 Equivalent & Substitute Parts

Part Overview

The STN749 is a PNP bipolar junction transistor manufactured by STMicroelectronics, rated for 25 V collector-emitter breakdown voltage and 3 A maximum collector current in a surface mount SOT-223 package. This component is classified as obsolete, making identification of functionally equivalent alternatives necessary for ongoing design support and production continuity. The STN749 delivers 1.6 W maximum power dissipation with a minimum DC current gain of 100 at 1 A collector current and 2 V collector-emitter voltage.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Voltage - Collector Emitter Breakdown (Max)	25	V
Current - Collector (Ic) (Max)	3	A
Power - Max	1.6	W
Vce Saturation (Max) @ Ib, Ic	600mV @ 300mA, 3A	—
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 1A, 2V	—
Current - Collector Cutoff (Max)	100nA	—
Package / Case	TO-261-4, TO-261AA (SOT-223)	—
Mounting Type	Surface Mount	—
Operating Temperature (Max)	150	°C
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the STN749 is determined by strict equivalence across the following critical parameters:

Primary Substitution Criteria:

Transistor Type: PNP (required)
Voltage - Collector Emitter Breakdown (Max): 25 V minimum
Current - Collector (Ic) (Max): 3 A minimum
Package / Case: TO-261-4, TO-261AA (SOT-223 form factor)
Mounting Type: Surface Mount
Vce Saturation characteristics compatible with application requirements
DC Current Gain (hFE) sufficient for circuit design

Direct Substitutes meet or exceed all primary criteria with identical or superior electrical performance and active product status.

Similar Substitutes meet primary electrical criteria but may have enhanced specifications (higher current rating, higher power dissipation, or higher transition frequency) or different product status classifications. These parts are electrically compatible but represent design upgrades rather than direct replacements.

Parameter Comparison

Parameter	STN749	FZT749TA	FZT749TC	FZT789ATA	FZT1149ATA	DPLS325E-13	PBSS303PZ,135	PBSS4032PZ,115
Manufacturer	STMicroelectronics	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated	Nexperia USA Inc.	Nexperia USA Inc.
Transistor Type	PNP	PNP	PNP	PNP	PNP	PNP	PNP	PNP
Voltage - Collector Emitter Breakdown (Max)	25 V	25 V	25 V	25 V	25 V	25 V	30 V	30 V
Current - Collector (Ic) (Max)	3 A	3 A	3 A	3 A	4 A	3 A	5.3 A	4.4 A
Power - Max	1.6 W	2 W	2 W	2 W	2.5 W	1 W	2 W	2 W
Vce Saturation (Max) @ Ib, Ic	600mV @ 300mA, 3A	600mV @ 300mA, 3A	600mV @ 300mA, 3A	500mV @ 100mA, 3A	350mV @ 140mA, 4A	500mV @ 100mA, 3A	265mV @ 265mA, 5.3A	400mV @ 200mA, 4A
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 1A, 2V	100 @ 1A, 2V	100 @ 1A, 2V	300 @ 10mA, 2V	250 @ 500mA, 2V	300 @ 10mA, 2V	250 @ 1A, 2V	150 @ 2A, 2V
Current - Collector Cutoff (Max)	100nA	100nA	100nA	100nA	100nA	100nA	100nA	100nA
Frequency - Transition	—	160MHz	160MHz	100MHz	135MHz	100MHz	130MHz	130MHz
Operating Temperature (Max)	150°C	150°C	150°C	150°C	150°C	150°C	150°C	150°C
Package / Case	TO-261-4, TO-261AA	TO-261-4, TO-261AA	TO-261-4, TO-261AA	TO-261-4, TO-261AA	TO-261-4, TO-261AA	TO-261-4, TO-261AA	TO-261-4, TO-261AA	TO-261-4, TO-261AA
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Product Status	Obsolete	Active	Active	Active	Active	Obsolete	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

Direct Substitutes (Recommended for Replacement):

FZT749TA and FZT749TC are direct functional equivalents to the STN749. Both are manufactured by Diodes Incorporated and maintain identical electrical specifications for collector current (3 A), collector-emitter breakdown voltage (25 V), and saturation voltage characteristics. Both parts carry active product status, ensuring long-term availability and supply chain stability. FZT749TA is supplied in Cut Tape (CT) & Digi-Reel® packaging, while FZT749TC is supplied in Tape & Reel (TR) packaging. Both are ROHS3 compliant with MSL 1 rating. The primary distinction is packaging format; selection depends on assembly process requirements.

Similar Substitutes (Electrical Compatibility with Enhanced Specifications):

FZT789ATA, FZT1149ATA, PBSS303PZ,135, and PBSS4032PZ,115 are electrically compatible alternatives that exceed the STN749 specifications in one or more parameters:

FZT789ATA: Maintains 3 A collector current and 25 V breakdown voltage with improved saturation voltage characteristics (500mV vs. 600mV) and higher DC current gain (300 vs. 100). Active product status.
FZT1149ATA: Provides enhanced current capability (4 A vs. 3 A) and higher power dissipation (2.5 W vs. 1.6 W) while maintaining 25 V breakdown voltage. Active product status.
PBSS303PZ,135: Offers higher voltage rating (30 V vs. 25 V) and significantly higher current capability (5.3 A vs. 3 A). Includes automotive-grade qualification (AEC-Q100). Active product status.
PBSS4032PZ,115: Provides higher voltage rating (30 V vs. 25 V) and enhanced current capability (4.4 A vs. 3 A). Includes automotive-grade qualification (AEC-Q100). Active product status.

Obsolete Alternative (Not Recommended for New Designs):

DPLS325E-13 is classified as obsolete and should not be selected for new designs despite electrical compatibility. This part exhibits reduced power dissipation (1 W vs. 1.6 W) and lower transition frequency (100MHz vs. unspecified for STN749).

Selection Criteria Summary:

For direct replacement in existing designs, select FZT749TA or FZT749TC based on packaging requirements. For new designs or applications requiring enhanced performance margins, select FZT1149ATA, PBSS303PZ,135, or PBSS4032PZ,115. All recommended substitutes maintain ROHS3 compliance and MSL 1 rating. Automotive applications should prioritize PBSS303PZ,135 or PBSS4032PZ,115 due to AEC-Q100 qualification.

Frequently Asked Questions (FAQ)

Q: Can FZT749TA directly replace STN749 in existing circuit designs?

A: Yes. FZT749TA is a direct functional equivalent with identical electrical specifications for collector current (3 A), collector-emitter breakdown voltage (25 V), saturation voltage (600mV @ 300mA, 3A), and DC current gain (100 @ 1A, 2V). Both use SOT-223 surface mount packaging. The primary difference is packaging format (Cut Tape & Digi-Reel® vs. Tape & Reel). No circuit modifications are required.

Q: What is the difference between FZT749TA and FZT749TC?

A: Both parts are electrically identical with the same electrical specifications and active product status. The distinction is packaging: FZT749TA is supplied in Cut Tape (CT) & Digi-Reel® format, while FZT749TC is supplied in Tape & Reel (TR) format. Selection depends on assembly equipment compatibility and production volume requirements.

Q: Why would I select FZT1149ATA instead of FZT749TA?

A: FZT1149ATA provides enhanced performance specifications: 4 A maximum collector current (vs. 3 A), 2.5 W maximum power dissipation (vs. 2 W), and improved saturation voltage characteristics (350mV @ 140mA, 4A vs. 600mV @ 300mA, 3A). Selection is appropriate for applications requiring higher current handling or improved thermal performance while maintaining 25 V breakdown voltage compatibility.

Q: Are PBSS303PZ,135 and PBSS4032PZ,115 suitable for non-automotive applications?

A: Yes. Both parts are active products with ROHS3 compliance and MSL 1 rating suitable for general industrial and consumer applications. The automotive-grade qualification (AEC-Q100) represents an additional quality assurance level but does not restrict use in non-automotive designs. These parts offer higher voltage ratings (30 V vs. 25 V) and enhanced current capability compared to STN749.

Q: What is the significance of the 25 V collector-emitter breakdown voltage specification?

A: The 25 V rating represents the maximum voltage that can be applied between collector and emitter before transistor breakdown occurs. This specification determines circuit voltage compatibility. Substitutes with 25 V or higher ratings (such as PBSS303PZ,135 and PBSS4032PZ,115 at 30 V) are compatible with STN749 applications. Substitutes with lower ratings would not be acceptable.

Q: Why is product status (Active vs. Obsolete) important for component selection?

A: Active product status ensures long-term availability, consistent manufacturing processes, and supply chain reliability. Obsolete components face discontinuation risk and may experience supply constraints. For new designs, active products (FZT749TA, FZT749TC, FZT789ATA, FZT1149ATA, PBSS303PZ,135, PBSS4032PZ,115) are preferred. For legacy system support, active substitutes provide continuity when the original STN749 becomes unavailable.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed (FZT749TA, FZT749TC, FZT789ATA, FZT1149ATA, DPLS325E-13, PBSS303PZ,135, PBSS4032PZ,115) are ROHS3 compliant with MSL 1 (Unlimited) moisture sensitivity rating. This ensures compatibility with modern manufacturing processes and environmental regulations.

Q: What does DC Current Gain (hFE) specification mean for substitution?

A: DC Current Gain represents the amplification factor of the transistor. The STN749 specifies minimum hFE of 100 at 1 A collector current and 2 V collector-emitter voltage. Substitutes with equal or higher hFE values (such as FZT789ATA at 300 or PBSS303PZ,135 at 250) provide equivalent or improved circuit performance. Lower hFE values would require circuit redesign.

Q: Can I use DPLS325E-13 as a substitute?

A: DPLS325E-13 is electrically compatible but classified as obsolete. It exhibits reduced power dissipation (1 W vs. 1.6 W) and lower transition frequency (100MHz). For new designs or ongoing production, active alternatives (FZT749TA, FZT789ATA, FZT1149ATA, PBSS303PZ,135, PBSS4032PZ,115) are recommended to ensure supply continuity and manufacturing consistency.

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