ZTX618STOB Equivalent & Substitute Parts

Part Overview

The ZTX618STOB is a Bipolar (BJT) NPN transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. This component operates at a maximum collector current of 3.5 A with a collector-emitter breakdown voltage of 20 V and delivers 1 W maximum power dissipation. The device features a 140 MHz transition frequency and is housed in an E-Line (TO-92 compatible) through-hole package with formed leads.

The ZTX618STOB is classified as obsolete. Locating equivalent substitute parts is necessary to support ongoing maintenance, repair, and redesign efforts for legacy equipment and systems utilizing this component.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Current - Collector (Ic) (Max)	3.5	A
Voltage - Collector Emitter Breakdown (Max)	20	V
Vce Saturation (Max) @ Ib, Ic	255 mV @ 50 mA, 3.5 A	—
Current - Collector Cutoff (Max)	100	nA
DC Current Gain (hFE) (Min) @ Ic, Vce	300 @ 200 mA, 2 V	—
Power - Max	1	W
Frequency - Transition	140	MHz
Operating Temperature Range	-55 to 200	°C (TJ)
Mounting Type	Through Hole	—
Package / Case	E-Line-3, Formed Leads	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the ZTX618STOB is determined by electrical and mechanical parameter equivalence. The following criteria establish valid substitution:

Electrical Parameters (Must Match):

Transistor Type: NPN
Current - Collector (Ic) (Max): 3.5 A
Voltage - Collector Emitter Breakdown (Max): 20 V
Vce Saturation (Max) @ Ib, Ic: 255 mV @ 50 mA, 3.5 A
Current - Collector Cutoff (Max): 100 nA
DC Current Gain (hFE) (Min) @ Ic, Vce: 300 @ 200 mA, 2 V
Power - Max: 1 W
Frequency - Transition: 140 MHz
Operating Temperature Range: -55°C to 200°C (TJ)

Mechanical Parameters (Must Match):

Mounting Type: Through Hole
Package / Case: E-Line-3, Formed Leads
Supplier Device Package: E-Line (TO-92 compatible)

Compliance Parameters (Must Match):

RoHS Status: ROHS3 Compliant
Moisture Sensitivity Level (MSL): 1 (Unlimited)

Substitute parts identified in this reference maintain identical electrical and mechanical specifications. Packaging format (bulk versus tape and box) does not affect functional equivalence.

Parameter Comparison

Parameter	ZTX618STOB	ZTX618STZ	Match
Manufacturer	Diodes Incorporated	Diodes Incorporated	✓
Transistor Type	NPN	NPN	✓
Current - Collector (Ic) (Max)	3.5 A	3.5 A	✓
Voltage - Collector Emitter Breakdown (Max)	20 V	20 V	✓
Vce Saturation (Max) @ Ib, Ic	255 mV @ 50 mA, 3.5 A	255 mV @ 50 mA, 3.5 A	✓
Current - Collector Cutoff (Max)	100 nA	100 nA	✓
DC Current Gain (hFE) (Min) @ Ic, Vce	300 @ 200 mA, 2 V	300 @ 200 mA, 2 V	✓
Power - Max	1 W	1 W	✓
Frequency - Transition	140 MHz	140 MHz	✓
Operating Temperature Range	-55°C to 200°C (TJ)	-55°C to 200°C (TJ)	✓
Mounting Type	Through Hole	Through Hole	✓
Package / Case	E-Line-3, Formed Leads	E-Line-3, Formed Leads	✓
Supplier Device Package	E-Line (TO-92 compatible)	E-Line (TO-92 compatible)	✓
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	✓
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	✓
Product Status	Obsolete	Active	—
Packaging Format	Bulk	Tape & Box (TB)	—

Engineering Selection Recommendations

The ZTX618STZ is a direct electrical and mechanical equivalent to the ZTX618STOB. Both components are manufactured by Diodes Incorporated and share identical electrical specifications, operating parameters, and physical packaging characteristics.

Product Status Consideration: The ZTX618STOB is classified as obsolete, while the ZTX618STZ maintains active product status. For new designs, repair operations, and system maintenance, the ZTX618STZ is the appropriate selection.

Compliance and Certification: Both parts maintain ROHS3 compliance and carry identical moisture sensitivity ratings (MSL 1 - Unlimited). No compliance barriers exist for substitution.

Packaging Format: The primary difference between these parts is packaging format. The ZTX618STOB is supplied in bulk configuration, while the ZTX618STZ is supplied in Tape & Box (TB) format. This distinction affects inventory management and component handling but does not impact functional performance or electrical characteristics.

Frequently Asked Questions (FAQ)

Q: Can the ZTX618STZ replace the ZTX618STOB in existing circuit designs?

A: Yes. The ZTX618STZ is electrically and mechanically equivalent to the ZTX618STOB. All electrical parameters, operating ranges, and physical package specifications are identical. Direct substitution is supported without circuit modification.

Q: What is the difference between the ZTX618STOB and ZTX618STZ?

A: The components are electrically identical. The primary difference is packaging format: ZTX618STOB is supplied in bulk, while ZTX618STZ is supplied in Tape & Box (TB) format. Product status also differs—ZTX618STOB is obsolete, while ZTX618STZ is active.

Q: Are there any compliance or certification differences between these parts?

A: No. Both parts maintain ROHS3 compliance, carry identical moisture sensitivity ratings (MSL 1 - Unlimited), and share the same REACH and ECCN classifications.

Q: Why is the ZTX618STOB classified as obsolete?

A: The ZTX618STOB has been discontinued by the manufacturer. The ZTX618STZ remains in active production and serves as the current equivalent for this device family.

Q: Can I use the ZTX618STZ in through-hole PCB applications?

A: Yes. The ZTX618STZ is a through-hole component with E-Line-3 formed leads, identical to the ZTX618STOB. It is suitable for through-hole PCB assembly without modification to existing board designs.

Q: What is the maximum collector current rating for these transistors?

A: Both the ZTX618STOB and ZTX618STZ are rated for a maximum collector current (Ic) of 3.5 A.

Q: What is the operating temperature range for these components?

A: Both parts operate across a junction temperature range of -55°C to 200°C (TJ).

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