ZTX455STOA Equivalent & Substitute Parts

Part Overview

The ZTX455STOA is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. This device features a 140 V collector-emitter breakdown voltage, 1 A maximum collector current, and 1 W power dissipation capability in a through-hole E-Line (TO-92 compatible) package.

The ZTX455STOA is classified as obsolete. Equivalent and substitute parts are necessary to maintain design continuity and ensure component availability for production, repair, and field replacement applications. Substitute devices must satisfy the electrical and mechanical requirements of the original specification while maintaining functional compatibility within the circuit design.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	140	V
Current - Collector (Ic) (Max)	1	A
Power - Max	1	W
Frequency - Transition	100	MHz
Mounting Type	Through Hole	—
Package / Case	E-Line-3, Formed Leads (TO-92 compatible)	—
Operating Temperature Range	-55 to 200	°C
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the ZTX455STOA is determined by the following critical parameters:

Primary Substitution Criteria:

Transistor Type: NPN
Voltage - Collector Emitter Breakdown (Max): ≥ 140 V
Current - Collector (Ic) (Max): ≥ 1 A
Power - Max: ≥ 1 W
Mounting Type: Through Hole
Package / Case: E-Line-3 or TO-92-3 compatible

Secondary Compatibility Factors:

Frequency - Transition: ≥ 100 MHz
Operating Temperature Range: Must encompass application requirements
RoHS and REACH compliance status

Substitute parts are grouped into two categories:

Category 1: Direct Equivalent (Same Base Specifications) The ZTX455STZ maintains identical electrical specifications to the ZTX455STOA. The only difference is packaging format (Cut Tape versus bulk). This part is functionally interchangeable.

Category 2: Functional Substitutes (Reduced Current Rating) The 2N5550 and 2N5551 series devices feature reduced maximum collector current (600 mA versus 1 A) and reduced power dissipation (625 mW versus 1 W). These parts are suitable for applications where the full 1 A current capability is not required. The 2N5551 series provides higher voltage rating (160 V) and lower saturation voltage characteristics.

Parameter Comparison

Parameter	ZTX455STOA	ZTX455STZ	2N5550TA	2N5550TAR	2N5550TFR	2N5551TA	2N5551TF	2N5551TFR
Manufacturer	Diodes Inc.	Diodes Inc.	Fairchild Semi.	onsemi	Fairchild Semi.	onsemi	onsemi	onsemi
Transistor Type	NPN	NPN	NPN	NPN	NPN	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	140 V	140 V	140 V	140 V	140 V	160 V	160 V	160 V
Current - Collector (Ic) (Max)	1 A	1 A	600 mA	600 mA	600 mA	600 mA	600 mA	600 mA
Power - Max	1 W	1 W	625 mW	625 mW	625 mW	625 mW	625 mW	625 mW
Frequency - Transition	100 MHz	100 MHz	300 MHz	300 MHz	300 MHz	100 MHz	100 MHz	100 MHz
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	E-Line-3	E-Line-3	TO-92-3	TO-92-3	TO-92-3	TO-92-3	TO-92-3	TO-92-3
Operating Temperature (Max)	200°C	200°C	150°C	150°C	150°C	150°C	150°C	150°C
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	—	ROHS3 Compliant	—	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Preferred): The ZTX455STZ is the primary substitute for the ZTX455STOA. Both devices are manufactured by Diodes Incorporated and maintain identical electrical specifications. The ZTX455STZ is in active production status, ensuring long-term availability. Selection between these parts depends on packaging requirements: ZTX455STZ is supplied in Cut Tape format, while the original ZTX455STOA was supplied in bulk. Both are ROHS3 compliant and suitable for applications requiring the full 1 A collector current and 1 W power dissipation.

For Current-Limited Applications: The 2N5550 series (2N5550TA, 2N5550TAR, 2N5550TFR) and 2N5551 series (2N5551TA, 2N5551TF, 2N5551TFR) are functional substitutes for applications where collector current does not exceed 600 mA and power dissipation remains below 625 mW. These devices are manufactured by established semiconductor suppliers (Fairchild Semiconductor and onsemi) and maintain active production status.

Voltage Considerations: The 2N5550 series maintains the 140 V collector-emitter breakdown voltage specification. The 2N5551 series provides enhanced voltage rating at 160 V, suitable for applications requiring additional voltage margin.

Temperature Considerations: The ZTX455STOA and ZTX455STZ support operating temperatures to 200°C. The 2N5550 and 2N5551 series are rated to 150°C maximum junction temperature. Applications requiring operation above 150°C must use the ZTX455STZ.

Compliance Status: All substitute parts maintain ROHS3 compliance and REACH unaffected status, consistent with the original ZTX455STOA specification.

Frequently Asked Questions (FAQ)

Q: Can the ZTX455STZ be used as a direct replacement for the ZTX455STOA?

A: Yes. The ZTX455STZ is electrically and mechanically equivalent to the ZTX455STOA. Both devices feature identical collector current (1 A), voltage rating (140 V), power dissipation (1 W), and transition frequency (100 MHz). The difference is packaging format: ZTX455STZ is supplied in Cut Tape, while ZTX455STOA was supplied in bulk. Both are through-hole E-Line (TO-92 compatible) packages.

Q: What is the difference between the 2N5550 and 2N5551 series?

A: The 2N5551 series provides a higher collector-emitter breakdown voltage (160 V versus 140 V) and lower saturation voltage characteristics. Both series are limited to 600 mA maximum collector current and 625 mW power dissipation. The 2N5551 is suitable for applications requiring enhanced voltage margin or lower saturation voltage performance.

Q: Can I use a 2N5550 or 2N5551 in place of the ZTX455STOA?

A: The 2N5550 and 2N5551 series are functional substitutes only for applications where the collector current requirement does not exceed 600 mA and power dissipation remains below 625 mW. The ZTX455STOA is rated for 1 A collector current and 1 W power dissipation. If your circuit requires the full 1 A capability, use the ZTX455STZ instead.

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

A: The ZTX455STZ maintains the E-Line-3 package format. The 2N5550 and 2N5551 series are supplied in TO-92-3 (TO-226-3) packages. While both package types are through-hole with compatible lead configurations, physical dimensions and lead spacing may differ. Verify PCB footprint compatibility before substitution.

Q: What is the maximum operating temperature for each substitute?

A: The ZTX455STOA and ZTX455STZ support junction temperatures to 200°C. The 2N5550 and 2N5551 series are rated to 150°C maximum junction temperature. For applications requiring operation above 150°C, the ZTX455STZ is the appropriate choice.

Q: Are all substitute parts RoHS compliant?

A: The ZTX455STOA, ZTX455STZ, 2N5550TAR, 2N5551TA, 2N5551TF, and 2N5551TFR are ROHS3 compliant. The 2N5550TA and 2N5550TFR do not specify RoHS status in the provided data. Verify RoHS compliance requirements for your application before selection.

Q: What is the inventory status of each substitute part?

A: The ZTX455STZ has 2210 units in stock. The 2N5550TA has 34767 units, 2N5550TAR has 47300 units, and 2N5550TFR has 22400 units. The 2N5551TA has 6370 units, 2N5551TF has 49944 units, and 2N5551TFR has 8408 units. All substitute parts are in active production and available for immediate procurement.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message