ZTX855STOB Equivalent & Substitute Parts

Part Overview

The ZTX855STOB is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. This device features a 150 V collector-emitter breakdown voltage rating with a maximum collector current of 4 A and operates across a temperature range of -55°C to 200°C. The ZTX855STOB is classified as an obsolete product, necessitating identification of equivalent substitute components for ongoing design support and procurement continuity. Active alternatives with identical electrical and mechanical specifications are available from the same manufacturer.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Current - Collector (Ic) Max	4	A
Voltage - Collector Emitter Breakdown (Max)	150	V
Vce Saturation (Max)	260 mV @ 400 mA, 4 A	—
Current - Collector Cutoff (Max)	50	nA
DC Current Gain (hFE) Min	100 @ 1 A, 5 V	—
Power - Max	1.2	W
Frequency - Transition	90	MHz
Operating Temperature Range	-55 to 200	°C
Mounting Type	Through Hole	—
Package / Case	E-Line-3	—
Supplier Device Package	E-Line (TO-92 compatible)	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the ZTX855STOB is determined by strict equivalence across all critical electrical and mechanical parameters. The substitute parts ZTX855 and ZTX855STZ maintain identical specifications for collector current (4 A maximum), collector-emitter breakdown voltage (150 V maximum), saturation voltage (260 mV @ 400 mA, 4 A), DC current gain (100 minimum @ 1 A, 5 V), transition frequency (90 MHz), power dissipation (1.2 W maximum), and operating temperature range (-55°C to 200°C). Both substitute parts utilize the same E-Line-3 package with TO-92 compatible pinout and through-hole mounting configuration. All three parts maintain ROHS3 compliance, unlimited moisture sensitivity rating (MSL 1), and identical regulatory classifications (REACH Unaffected, ECCN EAR99, HTSUS 8541.29.0075).

The primary distinction between substitute options lies in product status and packaging format. The ZTX855 is supplied in bulk packaging and maintains active product status. The ZTX855STZ is supplied in Tape & Box (TB) format and also maintains active product status with significantly higher inventory availability.

Parameter Comparison

Parameter	ZTX855STOB (Main)	ZTX855 (Substitute)	ZTX855STZ (Substitute)
Manufacturer	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated
Transistor Type	NPN	NPN	NPN
Current - Collector (Ic) Max	4 A	4 A	4 A
Voltage - Collector Emitter Breakdown (Max)	150 V	150 V	150 V
Vce Saturation (Max)	260 mV @ 400 mA, 4 A	260 mV @ 400 mA, 4 A	260 mV @ 400 mA, 4 A
Current - Collector Cutoff (Max)	50 nA	50 nA	50 nA
DC Current Gain (hFE) Min	100 @ 1 A, 5 V	100 @ 1 A, 5 V	100 @ 1 A, 5 V
Power - Max	1.2 W	1.2 W	1.2 W
Frequency - Transition	90 MHz	90 MHz	90 MHz
Operating Temperature Range	-55°C to 200°C	-55°C to 200°C	-55°C to 200°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	E-Line-3	E-Line-3	E-Line-3
Supplier Device Package	E-Line (TO-92 compatible)	E-Line (TO-92 compatible)	E-Line (TO-92 compatible)
Product Status	Obsolete	Active	Active
Packaging Format	—	Bulk	Tape & Box (TB)
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

Both ZTX855 and ZTX855STZ provide direct electrical and mechanical equivalence to the obsolete ZTX855STOB. Selection between the two active alternatives depends on procurement and assembly requirements rather than electrical performance.

The ZTX855 in bulk packaging is suitable for applications requiring manual component handling or custom packaging workflows. The ZTX855STZ in Tape & Box format is optimized for automated assembly processes and high-volume production environments. The ZTX855STZ offers significantly higher inventory availability (111,900 pieces) compared to the ZTX855 (4,150 pieces), providing superior supply chain continuity for sustained production requirements.

Both substitute parts maintain full ROHS3 compliance and identical regulatory certifications (REACH Unaffected, ECCN EAR99, HTSUS 8541.29.0075), ensuring compatibility with environmental and export control requirements applicable to the original ZTX855STOB.

Frequently Asked Questions (FAQ)

Q: Can ZTX855 and ZTX855STZ be used interchangeably with ZTX855STOB in existing circuit designs?

A: Yes. Both substitute parts maintain identical electrical specifications across all critical parameters including collector current (4 A), breakdown voltage (150 V), saturation voltage (260 mV), DC current gain (100 minimum), and operating temperature range (-55°C to 200°C). The E-Line-3 package with TO-92 compatible pinout ensures mechanical compatibility with existing PCB layouts and through-hole assembly processes.

Q: What is the difference between ZTX855 and ZTX855STZ?

A: The electrical and mechanical specifications are identical. The primary difference is packaging format: ZTX855 is supplied in bulk packaging, while ZTX855STZ is supplied in Tape & Box (TB) format for automated assembly. ZTX855STZ also offers significantly higher inventory availability.

Q: Why is the ZTX855STOB classified as obsolete?

A: The ZTX855STOB has been discontinued by the manufacturer. However, active equivalent parts with identical specifications remain available from Diodes Incorporated, ensuring design continuity and component availability.

Q: Are there any compliance or regulatory differences between the three part numbers?

A: No. All three parts maintain identical RoHS3 compliance status, REACH Unaffected classification, ECCN EAR99 designation, and HTSUS code 8541.29.0075. Moisture sensitivity level is identical at MSL 1 (Unlimited) for all variants.

Q: Which substitute part should be selected for new production designs?

A: For new production designs, ZTX855STZ is recommended due to active product status, Tape & Box packaging compatibility with automated assembly, and superior inventory availability. ZTX855 in bulk packaging remains available for applications with specific packaging requirements.

Q: Are the thermal and frequency characteristics identical across all three part numbers?

A: Yes. All three parts share identical transition frequency (90 MHz), maximum power dissipation (1.2 W), and operating temperature range (-55°C to 200°C). Thermal performance and high-frequency response are equivalent across ZTX855STOB, ZTX855, and ZTX855STZ.

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