ZTX749 Equivalent & Substitute Parts

Part Overview

The ZTX749 is a PNP bipolar junction transistor manufactured by onsemi, rated for 25 V collector-emitter breakdown voltage and 2 A maximum collector current. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for ongoing design requirements and procurement needs. The ZTX749 is packaged in TO-226-3 (TO-92-3) through-hole configuration and operates across a temperature range of -55°C to 150°C.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Current - Collector (Ic) (Max)	2	A
Voltage - Collector Emitter Breakdown (Max)	25	V
Vce Saturation (Max)	500	mV @ 200mA, 2A
Current - Collector Cutoff (Max)	100	nA
DC Current Gain (hFE) (Min)	100	@ 1A, 2V
Power - Max	1	W
Frequency - Transition	100	MHz
Operating Temperature	-55 to 150	°C
Mounting Type	Through Hole	—
Package / Case	TO-226-3, TO-92-3	—

Substitute Part Grouping Explanation

Substitution of the ZTX749 is determined by the following critical electrical and mechanical parameters:

Mandatory Matching Parameters:

Transistor Type: PNP
Voltage - Collector Emitter Breakdown (Max): 25 V
Current - Collector (Ic) (Max): 2 A minimum
Vce Saturation (Max): 500 mV or lower
Current - Collector Cutoff (Max): 100 nA or lower
DC Current Gain (hFE) (Min): 100 or higher
Power - Max: 1 W
Mounting Type: Through Hole
Package / Case: TO-92 compatible or E-Line (TO-92 compatible)

Acceptable Parameter Variations:

Frequency - Transition: 100 MHz or higher
Operating Temperature: -55°C minimum and 150°C or higher maximum
Product Status: Active preferred for long-term availability

The ZTX749 (onsemi, obsolete) has direct equivalents and similar substitutes from Diodes Incorporated, all rated for 25 V and featuring through-hole E-Line packaging compatible with TO-92 footprints.

Parameter Comparison

Parameter	ZTX749 (onsemi)	ZTX749 (Diodes Inc.)	ZTX1149A (Diodes Inc.)	ZTX789A (Diodes Inc.)
Transistor Type	PNP	PNP	PNP	PNP
Current - Collector (Ic) (Max)	2 A	2 A	3 A	3 A
Voltage - Collector Emitter Breakdown (Max)	25 V	25 V	25 V	25 V
Vce Saturation (Max)	500 mV @ 200mA, 2A	500 mV @ 200mA, 2A	300 mV @ 70mA, 3A	500 mV @ 100mA, 3A
Current - Collector Cutoff (Max)	100 nA	100 nA	100 nA	100 nA
DC Current Gain (hFE) (Min)	100 @ 1A, 2V	100 @ 1A, 2V	250 @ 500mA, 2V	300 @ 10mA, 2V
Power - Max	1 W	1 W	1 W	1 W
Frequency - Transition	100 MHz	160 MHz	135 MHz	100 MHz
Operating Temperature	-55 to 150°C	-55 to 200°C	-55 to 200°C	-55 to 200°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	TO-226-3, TO-92-3	E-Line (TO-92 compatible)	E-Line (TO-92 compatible)	E-Line (TO-92 compatible)
Product Status	Obsolete	Active	Active	Active
RoHS Status	—	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Direct Equivalent (Preferred for Pin-Compatible Replacement):

The ZTX749 from Diodes Incorporated is the direct equivalent to the obsolete onsemi ZTX749. This part maintains identical electrical specifications (2 A, 25 V, 100 mV saturation voltage, 100 MHz transition frequency) and is packaged in E-Line (TO-92 compatible) through-hole configuration. The Diodes Incorporated version is active and ROHS3 compliant, providing long-term availability and regulatory compliance advantages over the obsolete onsemi original.

Higher Current Capacity Substitutes:

The ZTX1149A and ZTX789A are similar PNP transistors rated for 3 A maximum collector current, exceeding the ZTX749 specification of 2 A. Both maintain the 25 V collector-emitter breakdown voltage and 1 W power rating. These parts are suitable for applications where the ZTX749 operates below its 2 A maximum rating and where increased current headroom is beneficial. Both are active, ROHS3 compliant, and feature extended operating temperature ranges (-55°C to 200°C).

Compliance and Availability:

All Diodes Incorporated substitutes are ROHS3 compliant and REACH unaffected, meeting modern regulatory requirements. The onsemi ZTX749 is classified as obsolete; transition to active Diodes Incorporated equivalents ensures continued procurement viability and supply chain stability.

Frequently Asked Questions (FAQ)

Q: Can the ZTX749 (Diodes Incorporated) directly replace the ZTX749 (onsemi)?

A: Yes. Both parts are electrically identical with matching specifications for collector current (2 A), collector-emitter breakdown voltage (25 V), saturation voltage (500 mV), and transition frequency (100 MHz). The Diodes Incorporated version uses E-Line (TO-92 compatible) packaging, which is footprint-compatible with the original TO-226-3 through-hole configuration. The primary advantage is active product status and ROHS3 compliance.

Q: When should ZTX1149A or ZTX789A be used instead of the direct ZTX749 equivalent?

A: ZTX1149A and ZTX789A are suitable when circuit design permits higher collector current ratings (3 A versus 2 A). These parts provide increased current margin and are preferred in applications where the ZTX749 operates near its maximum 2 A specification. Both maintain the 25 V voltage rating and 1 W power dissipation limit. Selection between ZTX1149A and ZTX789A depends on specific DC current gain and saturation voltage requirements at your operating point.

Q: Are there package compatibility concerns when substituting these parts?

A: All substitute parts use E-Line (TO-92 compatible) through-hole packaging. This packaging is mechanically and electrically compatible with standard TO-92 footprints and breadboards. The original ZTX749 (onsemi) used TO-226-3 (TO-92-3) packaging. E-Line packages are designed for direct substitution in TO-92 applications without PCB layout modifications.

Q: What is the temperature operating range difference, and does it matter?

A: The original ZTX749 (onsemi) operates from -55°C to 150°C. All Diodes Incorporated substitutes extend the upper limit to 200°C. This extended range provides additional thermal margin in high-temperature applications but does not restrict use in applications within the original -55°C to 150°C range. The extended range is a performance advantage with no compatibility penalty.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All Diodes Incorporated substitutes (ZTX749, ZTX1149A, ZTX789A) are ROHS3 compliant. The original onsemi ZTX749 does not specify RoHS status. ROHS3 compliance ensures compliance with current environmental and regulatory standards for electronic components.

Q: What is the difference in DC current gain (hFE) between these parts?

A: The original ZTX749 specifies hFE minimum of 100 @ 1A, 2V. ZTX1149A specifies 250 @ 500mA, 2V, and ZTX789A specifies 300 @ 10mA, 2V. These specifications are measured at different operating points. Higher hFE values indicate greater amplification capability at lower base currents. Selection depends on your specific bias point and base drive requirements.

Q: Can I use ZTX1149A or ZTX789A in a circuit designed for ZTX749?

A: Yes, provided the circuit does not depend on the exact 2 A maximum current limit. Both higher-current parts are backward compatible in applications where the ZTX749 operates below 2 A. The 25 V voltage rating, 1 W power dissipation, and through-hole mounting are identical. Verify that the higher DC current gain does not affect circuit biasing or frequency response in your specific application.

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