ZTX550STZ Equivalent & Substitute Parts

Part Overview

The ZTX550STZ is a PNP bipolar junction transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. This device features a maximum collector current of 1 A, collector-emitter breakdown voltage of 45 V, and a maximum power dissipation of 1 W. The transistor is housed in an E-Line (TO-92 compatible) through-hole package with formed leads.

The ZTX550STZ is classified as an obsolete product. Identification of equivalent and substitute parts is necessary to support ongoing maintenance, repair, and redesign activities for legacy systems and applications currently utilizing this component.

Substiute Parts

ZTX550STZ

Diodes IncorporatedIn Stock: 3219ZTX550STZ Datasheet

Current PartRFQ

ZTX551STZ

Diodes IncorporatedIn Stock: 29251ZTX551STZ Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the ZTX550STZ is determined by the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

• Transistor type must be PNP
• Maximum collector current must be greater than or equal to 1 A
• Maximum collector-emitter breakdown voltage must be greater than or equal to 45 V
• Maximum power dissipation must be greater than or equal to 1 W
• Transition frequency must be greater than or equal to 150 MHz
• Operating temperature range must encompass -55°C to 200°C

Mechanical Compatibility Criteria:

• Mounting type must be through-hole
• Package must be E-Line-3 with formed leads (TO-92 compatible)

The ZTX551STZ meets all substitution criteria. This part is manufactured by the same supplier (Diodes Incorporated), shares identical mechanical packaging, and exceeds the electrical specifications of the ZTX550STZ while maintaining full parameter compatibility.

Parameter Comparison

Engineering Selection Recommendations

The ZTX551STZ is the direct substitute for the obsolete ZTX550STZ. Both devices are manufactured by Diodes Incorporated and share identical mechanical packaging and thermal operating range. The ZTX551STZ is currently in active production status, ensuring long-term availability and supply chain continuity.

Both parts maintain ROHS3 compliance and REACH unaffected status, satisfying regulatory requirements for new designs and legacy system support. The ZTX551STZ provides enhanced electrical performance with a higher collector-emitter breakdown voltage (60 V versus 45 V), making it suitable for applications requiring greater voltage margin while maintaining compatibility with existing circuit designs rated for the ZTX550STZ.

The primary electrical difference is the DC current gain specification: the ZTX550STZ specifies a minimum hFE of 100 at 150 mA and 10 V, while the ZTX551STZ specifies a minimum hFE of 50 at the same conditions. Circuit designs dependent on higher current gain should account for this parameter variation during implementation.

Frequently Asked Questions (FAQ)

Q: Can the ZTX551STZ be used as a direct replacement for the ZTX550STZ in existing applications?

A: The ZTX551STZ is mechanically and electrically compatible with the ZTX550STZ. Both devices share identical through-hole E-Line-3 packaging, maximum collector current (1 A), maximum power dissipation (1 W), transition frequency (150 MHz), and operating temperature range (-55°C to 200°C). The ZTX551STZ provides higher collector-emitter breakdown voltage (60 V versus 45 V), which is advantageous for voltage margin. However, the lower DC current gain specification (50 versus 100) must be evaluated against circuit design requirements.

Q: What are the key differences between the ZTX550STZ and ZTX551STZ?

A: The primary differences are: (1) Collector-emitter breakdown voltage: ZTX550STZ is 45 V, ZTX551STZ is 60 V; (2) DC current gain (hFE): ZTX550STZ minimum is 100, ZTX551STZ minimum is 50; (3) Vce saturation: ZTX550STZ is 250 mV, ZTX551STZ is 350 mV; (4) Product status: ZTX550STZ is obsolete, ZTX551STZ is active. All other electrical and mechanical parameters are identical.

Q: Are both parts available in the same package?

A: Yes. Both the ZTX550STZ and ZTX551STZ are housed in E-Line-3 packages with formed leads, compatible with TO-92 footprints. Both are through-hole mounted components with identical lead configurations.

Q: What is the significance of the product status difference?

A: The ZTX550STZ is classified as obsolete, indicating discontinued production and limited future availability. The ZTX551STZ is in active production status, ensuring reliable supply chain access and long-term component availability for new designs and ongoing system support.

Q: Do both parts meet current regulatory compliance standards?

A: Yes. Both the ZTX550STZ and ZTX551STZ are ROHS3 compliant and REACH unaffected, satisfying current regulatory requirements for electronic component manufacturing and use.

Q: Which part should be selected for new circuit designs?

A: The ZTX551STZ should be selected for new designs due to its active production status, higher voltage rating, and regulatory compliance. The ZTX550STZ should be used only for legacy system maintenance and repair where existing circuit designs are specifically validated for this component.