ZTX325STZ Equivalent & Substitute Parts

Part Overview

The ZTX325STZ is an RF transistor NPN manufactured by Diodes Incorporated, designed for RF applications operating at 1.3GHz with a maximum collector-emitter breakdown voltage of 15V and power dissipation of 350mW. The device is packaged in a Through Hole E-Line (TO-92 compatible) configuration and is classified as obsolete. Due to its obsolete status, equivalent and substitute parts are necessary for ongoing design support, production continuity, and system maintenance where RF transistor functionality is required.

Substiute Parts

ZTX325STZ

Diodes IncorporatedIn Stock: 1147ZTX325STZ Datasheet

Current PartRFQ

BF776H6327XTSA1

Infineon TechnologiesIn Stock: 1511BF776H6327XTSA1 Datasheet

MFR RecommendedRFQ

BFU690F,115

NXP USA Inc.In Stock: 36429BFU690F,115 Datasheet

MFR RecommendedRFQ

CPH6001A-TL-E

onsemiIn Stock: 17326CPH6001A-TL-E Datasheet

MFR RecommendedRFQ

MAPR-002729-170M00

MACOM Technology SolutionsIn Stock: 857MAPR-002729-170M00 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the ZTX325STZ is determined by the following critical parameters: transistor type (NPN), maximum collector-emitter breakdown voltage, maximum power dissipation, maximum collector current, and operating frequency capability. The substitute parts listed below are grouped based on their ability to meet or exceed the electrical specifications of the original device while maintaining NPN transistor functionality.

The key substitution criteria are:

• Transistor Type: NPN (mandatory match)
• Voltage Rating: Minimum 15V collector-emitter breakdown voltage
• Power Dissipation: Minimum 350mW capability
• Collector Current: Minimum 50mA capability
• Frequency Response: Capability at or above 1.3GHz
• RoHS3 Compliance: Required for regulatory alignment
• Product Status: Active or available inventory preferred

Parameter Comparison

Engineering Selection Recommendations

BF776H6327XTSA1 (Infineon Technologies): This part is an active product with ROHS3 compliance. It provides higher frequency capability (46GHz) and maintains the 50mA collector current maximum. However, the voltage rating (4.7V) is significantly lower than the ZTX325STZ (15V), making it unsuitable for applications requiring the original 15V rating. Mounting type is surface mount (SOT-343), requiring PCB redesign from the original through-hole configuration.

BFU690F,115 (NXP USA Inc.): This active product offers ROHS3 compliance with 18GHz frequency capability and 100mA collector current capacity. The voltage rating (5.5V) remains below the original 15V specification. Power dissipation (230mW) is lower than the original 350mW. Surface mount packaging (SOT-343F) requires PCB layout modification. High inventory availability (36,400 pcs) supports production continuity.

CPH6001A-TL-E (onsemi): This active product provides ROHS3 compliance with 12V voltage rating, approaching the original 15V specification. Power dissipation (800mW) exceeds the original 350mW, providing design margin. Frequency capability (6.7GHz) exceeds the original 1.3GHz requirement. Collector current capacity (100mA) exceeds the original 50mA. Surface mount packaging (SOT-23-6) requires PCB redesign. Operating temperature maximum (150°C) is lower than the original 200°C.

MAPR-002729-170M00 (MACOM Technology Solutions): This active product offers ROHS3 compliance with the highest voltage rating (65V) and power dissipation (170W) among all substitutes. Collector current capacity (27A) significantly exceeds the original 50mA. Operating temperature maximum (200°C) matches the original specification. Chassis mount packaging represents a fundamentally different form factor unsuitable for direct PCB substitution. Frequency specification is not provided. This part is applicable only for high-power RF applications with different mechanical constraints.

Frequently Asked Questions (FAQ)

Q: Can BF776H6327XTSA1 directly replace ZTX325STZ in existing designs?

A: Direct replacement is not recommended. While both are NPN RF transistors with 50mA maximum collector current, the BF776H6327XTSA1 has a maximum voltage rating of 4.7V compared to the ZTX325STZ's 15V. Additionally, the mounting type differs (surface mount SOT-343 versus through-hole E-Line), requiring PCB redesign. Applications operating at voltages above 4.7V will not function with this substitute.

Q: What are the voltage limitations when selecting a substitute?

A: The ZTX325STZ operates at a maximum collector-emitter breakdown voltage of 15V. Substitute parts must be rated for at least 15V to maintain voltage margin in the original application. BF776H6327XTSA1 (4.7V) and BFU690F,115 (5.5V) are unsuitable for applications requiring the full 15V rating. CPH6001A-TL-E (12V) approaches but does not fully meet the original specification. MAPR-002729-170M00 (65V) exceeds the requirement.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All listed substitute parts—BF776H6327XTSA1, BFU690F,115, CPH6001A-TL-E, and MAPR-002729-170M00—are ROHS3 compliant, matching the original ZTX325STZ compliance status.

Q: What mounting considerations apply to these substitutes?

A: The original ZTX325STZ uses through-hole E-Line (TO-92 compatible) packaging. BF776H6327XTSA1, BFU690F,115, and CPH6001A-TL-E are all surface mount devices, requiring PCB layout and assembly process modifications. MAPR-002729-170M00 uses chassis mount packaging, suitable only for discrete component mounting outside standard PCB assembly. Through-hole mounting is not available among the listed substitutes.

Q: How do frequency capabilities compare?

A: The ZTX325STZ operates at 1.3GHz transition frequency. All listed substitutes exceed this specification: BF776H6327XTSA1 (46GHz), BFU690F,115 (18GHz), and CPH6001A-TL-E (6.7GHz). MAPR-002729-170M00 does not specify transition frequency. Higher frequency capability does not guarantee compatibility; circuit design and impedance matching must be verified for the specific application.

Q: Which substitute offers the best power dissipation margin?

A: The ZTX325STZ is rated for 350mW maximum power dissipation. CPH6001A-TL-E provides the highest power rating (800mW) among small-signal substitutes, offering 2.3× margin. MAPR-002729-170M00 provides 170W, but its chassis mount form factor and high current capacity (27A) indicate application in fundamentally different power classes. BF776H6327XTSA1 (200mW) and BFU690F,115 (230mW) provide lower margins.

Q: What is the operating temperature range consideration?

A: The ZTX325STZ operates from -55°C to 200°C (TJ). BF776H6327XTSA1, BFU690F,115, and CPH6001A-TL-E are limited to 150°C maximum junction temperature, reducing the upper operating range by 50°C. MAPR-002729-170M00 matches the original 200°C maximum. Applications requiring the full -55°C to 200°C range will not function with the three surface-mount substitutes.

Q: Is CPH6001A-TL-E the most suitable general-purpose substitute?

A: CPH6001A-TL-E offers the closest electrical specification match for general RF applications: 12V voltage rating (approaching 15V), 6.7GHz frequency capability (exceeding 1.3GHz requirement), 800mW power dissipation (exceeding 350mW), and 100mA collector current (exceeding 50mA). However, surface mount packaging requires PCB redesign, and the 150°C maximum temperature is 50°C lower than the original. Application-specific requirements determine suitability.

Q: Can MAPR-002729-170M00 be used in place of ZTX325STZ?

A: MAPR-002729-170M00 is not a direct substitute. It is a high-power RF transistor (170W, 27A) in chassis mount packaging, designed for fundamentally different applications than the small-signal ZTX325STZ (350mW, 50mA). Transition frequency is not specified. Mechanical mounting, thermal management, and circuit design requirements are incompatible with the original application.