NZT749 Equivalent & Substitute Parts

Part Overview

The NZT749 is a PNP bipolar junction transistor manufactured by onsemi, rated for 25V collector-emitter breakdown voltage and 4A maximum collector current in a surface mount SOT-223-4 package. This component is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. The NZT749 operates across an extended temperature range of -55°C to 150°C and delivers 1.2W maximum power dissipation with a transition frequency of 75MHz.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Voltage - Collector Emitter Breakdown (Max)	25	V
Current - Collector (Ic) (Max)	4	A
Power - Max	1.2	W
Frequency - Transition	75	MHz
Operating Temperature Range	-55 to 150	°C
Package / Case	TO-261-4, TO-261AA	—
Mounting Type	Surface Mount	—
DC Current Gain (hFE) (Min) @ Ic, Vce	80 @ 1A, 2V	—
Vce Saturation (Max) @ Ib, Ic	300mV @ 100mA, 1A	—

Substitute Part Grouping Explanation

Substitution of the NZT749 is determined by strict alignment of electrical and mechanical parameters. The primary substitution criteria are:

Mandatory Matching Parameters:

Transistor Type: PNP (polarity must match)
Voltage - Collector Emitter Breakdown: minimum 25V
Current - Collector (Ic) (Max): minimum 4A
Package / Case: TO-261-4 or TO-261AA (physical compatibility)
Mounting Type: Surface Mount

Secondary Compatibility Parameters:

Operating Temperature Range: must encompass -55°C to 150°C
Power - Max: minimum 1.2W
Frequency - Transition: minimum 75MHz

Substitute parts are grouped into two categories based on these criteria:

Category A - Direct Electrical Equivalents (PNP, 25V, 4A):

FZT1149ATA: Matches transistor type, voltage, and current ratings with enhanced power handling (2.5W) and higher transition frequency (135MHz)
FZT749TA: Matches transistor type and voltage with slightly reduced current rating (3A) but enhanced power handling (2W) and higher transition frequency (160MHz)
FZT789ATA: Matches transistor type and voltage with reduced current rating (3A) and power handling (2W)

Category B - Non-Equivalent (Excluded from Substitution):

BSP60,115: PNP-Darlington type with incompatible current rating (1A maximum) and different saturation characteristics
FZT1049ATA / FZT1049ATC: NPN type (polarity mismatch with PNP requirement)

Parameter Comparison

Parameter	NZT749	FZT1149ATA	FZT749TA	FZT789ATA
Manufacturer	onsemi	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated
Transistor Type	PNP	PNP	PNP	PNP
Voltage - Collector Emitter Breakdown (Max)	25V	25V	25V	25V
Current - Collector (Ic) (Max)	4A	4A	3A	3A
Power - Max	1.2W	2.5W	2W	2W
Frequency - Transition	75MHz	135MHz	160MHz	100MHz
Operating Temperature Range	-55 to 150°C	-55 to 150°C	-55 to 150°C	-55 to 150°C
Package / Case	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
DC Current Gain (hFE) (Min) @ Ic, Vce	80 @ 1A, 2V	250 @ 500mA, 2V	100 @ 1A, 2V	300 @ 10mA, 2V
Vce Saturation (Max) @ Ib, Ic	300mV @ 100mA, 1A	350mV @ 140mA, 4A	600mV @ 300mA, 3A	500mV @ 100mA, 3A
Product Status	Obsolete	Active	Active	Active
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

FZT1149ATA is the primary substitute for the NZT749. This part maintains exact electrical specifications for transistor type (PNP), voltage rating (25V), and current rating (4A). The FZT1149ATA is manufactured by Diodes Incorporated with active product status, ensuring long-term availability and supply chain stability. The part carries ROHS3 compliance and meets AEC-Q101 automotive qualification standards. Enhanced power dissipation (2.5W versus 1.2W) and higher transition frequency (135MHz versus 75MHz) provide performance margin in the target application. Operating temperature range (-55°C to 150°C) matches the original specification.

FZT749TA serves as a secondary substitute when current requirements do not exceed 3A. This part maintains PNP polarity, 25V voltage rating, and offers superior transition frequency (160MHz) with active product status and ROHS3 compliance. The reduced current rating (3A maximum) and increased saturation voltage (600mV at 3A) require circuit-level evaluation.

FZT789ATA is suitable for applications with current requirements not exceeding 3A and where transition frequency of 100MHz is adequate. This part maintains PNP polarity and 25V voltage rating with active product status and ROHS3 compliance.

Parts with incompatible specifications (BSP60,115 with 1A current rating and Darlington configuration; FZT1049ATA and FZT1049ATC with NPN polarity) are not suitable substitutes.

Frequently Asked Questions (FAQ)

Q: Can the FZT1149ATA directly replace the NZT749 in existing designs?

A: Yes. The FZT1149ATA maintains identical transistor type (PNP), voltage rating (25V), and current rating (4A). Both components use the same package (TO-261-4, TO-261AA) and mounting type (surface mount). Pin compatibility and electrical characteristics support direct substitution without circuit modification.

Q: Why are FZT1049ATA and FZT1049ATC not suitable substitutes?

A: These parts are NPN transistors, while the NZT749 is PNP. Transistor polarity is a fundamental electrical characteristic that cannot be changed through circuit adaptation. NPN and PNP transistors have opposite collector-emitter current flow directions and require different biasing schemes. Substitution would require complete circuit redesign.

Q: What is the difference between FZT749TA and FZT1149ATA?

A: The FZT749TA has a maximum collector current of 3A, while the FZT1149ATA is rated for 4A. The FZT749TA exhibits higher saturation voltage (600mV at 3A) compared to the FZT1149ATA (350mV at 4A). Both maintain 25V voltage rating and PNP polarity. Selection depends on circuit current requirements and saturation voltage tolerance.

Q: Is the BSP60,115 a suitable substitute?

A: No. The BSP60,115 is a PNP-Darlington transistor with a maximum collector current of 1A, which is insufficient for the NZT749 specification of 4A. Additionally, Darlington transistors exhibit significantly different saturation characteristics (1.3V versus 300mV) and are not electrically equivalent to standard BJT transistors.

Q: What compliance certifications should I verify for substitute parts?

A: All recommended substitute parts (FZT1149ATA, FZT749TA, FZT789ATA) carry ROHS3 compliance. The FZT1149ATA additionally holds AEC-Q101 automotive qualification. Verify that selected substitutes meet your application's specific compliance requirements before implementation.

Q: Can I use FZT789ATA if my circuit only requires 3A?

A: Yes, provided the transition frequency of 100MHz meets your circuit requirements. The FZT789ATA maintains PNP polarity, 25V voltage rating, and 3A current rating. However, verify saturation voltage specifications (500mV at 3A) against your design margins, as this parameter differs from the NZT749 (300mV at 1A).

Q: Are there packaging differences between the NZT749 and its substitutes?

A: All substitute parts use the same package designation (TO-261-4, TO-261AA) and surface mount technology. Physical dimensions and pin configurations are compatible. Verify specific supplier device package designations (SOT-223-3 versus SOT-223-4) with your PCB layout to confirm footprint compatibility.

Q: Why is the NZT749 classified as obsolete?

A: Product obsolescence is determined by the manufacturer and reflects end-of-life status. The NZT749 is no longer in active production by onsemi. Active substitute parts from Diodes Incorporated ensure continued availability and supply chain reliability for new designs and production continuity.

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