ZTX657 Equivalent & Substitute Parts

Part Overview

The ZTX657 is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. This device operates at 300 V collector-emitter breakdown voltage with a maximum collector current of 500 mA and 1 W power dissipation capability. The ZTX657 is housed in an E-Line (TO-92 compatible) through-hole package and maintains Active product status with full RoHS3 compliance.

Equivalent and substitute parts become necessary when the primary part reaches end-of-life status, inventory constraints occur, or design requirements necessitate alternative electrical or thermal characteristics. The substitute parts listed maintain functional compatibility within specified electrical parameter ranges while accommodating different packaging formats and thermal ratings.

Key Parameters

Parameter	ZTX657 (Main Part)	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	300	V
Current - Collector (Ic) (Max)	500	mA
Power - Max	1	W
Frequency - Transition	30	MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	50 @ 100mA, 5V	—
Vce Saturation (Max) @ Ib, Ic	500mV @ 10mA, 100mA	—
Current - Collector Cutoff (Max)	100	nA
Operating Temperature Range	-55 to 200	°C
Mounting Type	Through Hole	—
Package / Case	E-Line-3 (TO-92 compatible)	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution compatibility for the ZTX657 is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

Transistor Type: NPN configuration required
Voltage - Collector Emitter Breakdown: Minimum 300 V (equal or greater)
Current - Collector (Ic) (Max): 500 mA (equal or greater)
Mounting Type: Through Hole
Package Compatibility: TO-92 or TO-92-3 form factors

Secondary Compatibility Factors:

Power dissipation capability
DC current gain (hFE) characteristics
Frequency response
Operating temperature range
RoHS and REACH compliance status

The substitute parts identified (2N6517BU, 2N6517TA, KSP42BU, and MPSA42) meet or exceed the primary electrical specifications of the ZTX657. Variations in secondary parameters reflect different design optimizations and manufacturing sources but do not preclude functional substitution within the specified electrical envelope.

Parameter Comparison

Parameter	ZTX657	2N6517BU	2N6517TA	KSP42BU	MPSA42	Unit
Transistor Type	NPN	NPN	NPN	NPN	NPN	—
Voltage - Collector Emitter Breakdown (Max)	300	350	350	300	300	V
Current - Collector (Ic) (Max)	500	500	500	500	500	mA
Power - Max	1	0.625	0.625	0.625	0.625	W
Frequency - Transition	30	200	200	50	50	MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	50 @ 100mA, 5V	20 @ 50mA, 10V	20 @ 50mA, 10V	40 @ 30mA, 10V	40 @ 30mA, 10V	—
Vce Saturation (Max) @ Ib, Ic	500mV @ 10mA, 100mA	1V @ 5mA, 50mA	1V @ 5mA, 50mA	500mV @ 2mA, 20mA	500mV @ 2mA, 20mA	—
Current - Collector Cutoff (Max)	100	50	50	100	100	nA
Operating Temperature Range	-55 to 200	to 150	to 150	to 150	-55 to 150	°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	—
Package / Case	E-Line-3	TO-92-3	TO-92-3	TO-92-3	TO-92	—
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	Not applicable	—

Engineering Selection Recommendations

2N6517BU (onsemi) - Last Time Buy Status

The 2N6517BU meets all primary electrical substitution criteria with 350 V breakdown voltage and 500 mA collector current. This part carries Last Time Buy product status, indicating limited future availability. Selection of this substitute should account for inventory planning and long-term supply chain considerations. RoHS3 compliance is confirmed.

2N6517TA (onsemi) - Active Status

The 2N6517TA is functionally equivalent to 2N6517BU with identical electrical specifications but supplied in Cut Tape (CT) packaging format. This part maintains Active product status with confirmed availability. RoHS3 compliance is confirmed. The formed leads configuration accommodates automated assembly processes.

KSP42BU (onsemi) - Active Status

The KSP42BU provides direct voltage and current compatibility at 300 V and 500 mA with Active product status. This part offers the highest inventory availability (105,200 pieces) among substitute options. Electrical characteristics match the ZTX657 across saturation voltage and cutoff current parameters. RoHS3 compliance is confirmed.

MPSA42 (Diotec Semiconductor) - Active Status

The MPSA42 meets primary electrical specifications with 300 V breakdown voltage and 500 mA collector current. This part maintains Active product status with substantial inventory (27,010 pieces). Operating temperature range extends to -55°C, matching the ZTX657 lower limit. RoHS compliance status is not applicable; REACH status is vendor undefined.

Frequently Asked Questions (FAQ)

Q: Can the ZTX657 be directly replaced with any of these substitute parts?

A: Direct replacement is possible within the specified electrical parameter envelope. All substitute parts maintain NPN configuration, 300 V or greater breakdown voltage, and 500 mA collector current capability. Physical package compatibility (TO-92 form factor) is confirmed across all substitutes. Verify circuit-specific requirements for power dissipation, frequency response, and operating temperature range before final selection.

Q: What is the primary difference between 2N6517BU and 2N6517TA?

A: Both parts are electrically identical with 350 V breakdown voltage and 200 MHz transition frequency. The primary difference is packaging format: 2N6517BU is supplied in Bulk packaging, while 2N6517TA is supplied in Cut Tape (CT) format with formed leads. The 2N6517TA is recommended for new designs due to Active product status, whereas 2N6517BU carries Last Time Buy designation.

Q: Why does the ZTX657 have higher power rating (1 W) than the substitute parts (0.625 W)?

A: The ZTX657 is rated for 1 W maximum power dissipation, while 2N6517BU, 2N6517TA, and KSP42BU are rated for 0.625 W. MPSA42 also carries 0.625 W rating. Applications requiring sustained power dissipation above 0.625 W must verify thermal management and duty cycle compatibility. The ZTX657 remains the preferred choice for high-power applications.

Q: Are all substitute parts RoHS3 compliant?

A: 2N6517BU, 2N6517TA, and KSP42BU are confirmed RoHS3 compliant. MPSA42 carries "Not applicable" RoHS status. For applications requiring RoHS3 compliance certification, select from the onsemi-manufactured substitutes (2N6517BU, 2N6517TA, or KSP42BU).

Q: What is the significance of the operating temperature range difference?

A: The ZTX657 operates from -55°C to 200°C, while most substitutes operate to 150°C maximum. MPSA42 extends to -55°C at the lower limit. Applications requiring operation above 150°C junction temperature must retain the ZTX657. For standard industrial temperature ranges (-55°C to 150°C), all substitutes are suitable.

Q: Which substitute part offers the best inventory availability?

A: KSP42BU provides the highest inventory availability with 105,200 pieces in stock. MPSA42 follows with 27,010 pieces. 2N6517TA maintains 8,200 pieces, and 2N6517BU has 20,200 pieces available. Inventory levels should be verified at time of procurement.

Q: Can MPSA42 be used in applications requiring REACH compliance documentation?

A: MPSA42 carries "Vendor Undefined" REACH status, which may not satisfy applications requiring explicit REACH compliance documentation. For applications with strict REACH compliance requirements, select 2N6517BU, 2N6517TA, or KSP42BU, all of which carry "REACH Unaffected" status.

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