ZTX451 Equivalent & Substitute Parts

Part Overview

The ZTX451 is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. This through-hole component operates at 60 V collector-emitter breakdown voltage with a maximum collector current of 1 A and 1 W power dissipation. The device is currently in active production status with 1445 units in stock. Substitute parts are identified when equivalent electrical performance and mechanical compatibility are required due to component availability, supply chain considerations, or design flexibility within specified parameter ranges.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	60	V
Current - Collector (Ic) (Max)	1	A
Power - Max	1	W
Frequency - Transition	150	MHz
Mounting Type	Through Hole	—
Package / Case	E-Line-3 (TO-92 compatible)	—
Operating Temperature (Max)	200	°C
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the ZTX451 is determined by strict equivalence in the following electrical and mechanical parameters:

Primary Substitution Criteria:

Transistor type must be NPN
Voltage - Collector Emitter Breakdown (Max) must be 60 V or greater
Current - Collector (Ic) (Max) must be 1 A or greater
Mounting type must be Through Hole
Package must be TO-92-3 or E-Line compatible
Operating temperature range must support the application requirement
RoHS3 compliance status must be maintained

Secondary Compatibility Factors:

Vce Saturation characteristics
DC Current Gain (hFE) specifications
Frequency - Transition performance
Power dissipation capability

The identified substitute parts KSD1616AGBU and KSC1008YBU meet the primary electrical and mechanical criteria for direct substitution within the specified parameter envelope.

Parameter Comparison

Parameter	ZTX451 (Diodes Inc.)	KSD1616AGBU (onsemi)	KSC1008YBU (Fairchild)
Transistor Type	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	60 V	60 V	60 V
Current - Collector (Ic) (Max)	1 A	1 A	700 mA
Power - Max	1 W	750 mW	800 mW
Frequency - Transition	150 MHz	160 MHz	50 MHz
Vce Saturation (Max)	350 mV @ 15mA, 150mA	300 mV @ 50mA, 1A	400 mV @ 50mA, 500mA
Current - Collector Cutoff (Max)	100 nA	100 nA	100 nA
DC Current Gain (hFE) (Min)	50 @ 150mA, 10V	200 @ 100mA, 2V	120 @ 50mA, 2V
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	E-Line-3 (TO-92 compatible)	TO-92-3	TO-92-3
Operating Temperature (Max)	200 °C	150 °C	150 °C
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Not specified

Engineering Selection Recommendations

KSD1616AGBU (onsemi) - Primary Substitute

The KSD1616AGBU provides the closest electrical equivalence to the ZTX451. Both devices support 1 A maximum collector current at 60 V breakdown voltage with through-hole TO-92-3 packaging. The KSD1616AGBU demonstrates superior DC current gain (200 vs. 50) and lower Vce saturation (300 mV vs. 350 mV), resulting in improved switching efficiency. Transition frequency is marginally higher at 160 MHz versus 150 MHz. The device maintains ROHS3 compliance. The primary design consideration is the reduced maximum operating temperature of 150 °C compared to the ZTX451's 200 °C rating; this substitution is suitable for applications operating within the 150 °C thermal envelope.

KSC1008YBU (Fairchild Semiconductor) - Secondary Substitute

The KSC1008YBU operates at the same 60 V breakdown voltage with through-hole TO-92-3 packaging. Maximum collector current is 700 mA, which is below the ZTX451's 1 A specification. This device is suitable for applications requiring collector currents not exceeding 700 mA. The transition frequency of 50 MHz is significantly lower than the ZTX451's 150 MHz, limiting use in higher-frequency switching applications. RoHS compliance status is not specified in available documentation. This substitute is applicable only when current requirements do not exceed 700 mA and frequency performance is not critical.

Compliance and Availability

Both substitute parts maintain active production status with substantial inventory availability. The KSD1616AGBU offers 5300 units in stock, while the KSC1008YBU provides 135885 units. Both devices carry EAR99 export classification and REACH unaffected status, matching the ZTX451's regulatory profile.

Frequently Asked Questions (FAQ)

Q: Can the KSD1616AGBU directly replace the ZTX451 in all applications?

A: The KSD1616AGBU is electrically compatible for applications operating within a maximum junction temperature of 150 °C. The ZTX451 supports operation to 200 °C. If your application requires sustained operation above 150 °C, the KSD1616AGBU is not suitable. For applications within the 150 °C thermal limit, the KSD1616AGBU provides equivalent or superior performance across all other electrical parameters.

Q: What is the primary limitation of the KSC1008YBU as a substitute?

A: The KSC1008YBU has a maximum collector current rating of 700 mA, compared to the ZTX451's 1 A. This device is suitable only for circuits designed to operate at or below 700 mA collector current. Additionally, the 50 MHz transition frequency is substantially lower than the ZTX451's 150 MHz, making it unsuitable for high-frequency switching applications.

Q: Are the package dimensions identical between the ZTX451 and substitute parts?

A: The ZTX451 uses an E-Line-3 package (TO-92 compatible), while both substitute parts use TO-92-3 packaging. These packages are mechanically compatible for through-hole mounting applications. Pin configuration and lead spacing are equivalent, allowing direct board-level substitution without layout modification.

Q: Do all three devices meet RoHS3 compliance requirements?

A: The ZTX451 and KSD1616AGBU are explicitly ROHS3 compliant. The KSC1008YBU's RoHS compliance status is not specified in the provided technical documentation. If RoHS3 compliance is a design requirement, the KSD1616AGBU is the recommended substitute.

Q: How do the DC current gain specifications differ between these devices?

A: The ZTX451 specifies a minimum hFE of 50 at 150 mA collector current and 10 V Vce. The KSD1616AGBU provides a minimum hFE of 200 at 100 mA and 2 V Vce, indicating superior current amplification. The KSC1008YBU specifies a minimum hFE of 120 at 50 mA and 2 V Vce. Higher hFE values reduce base drive requirements in switching applications.

Q: What is the significance of Vce saturation differences?

A: The ZTX451 exhibits 350 mV saturation voltage at specified test conditions, while the KSD1616AGBU shows 300 mV and the KSC1008YBU shows 400 mV. Lower saturation voltage reduces power dissipation in saturated switching modes. The KSD1616AGBU's lower saturation voltage provides improved efficiency in switching applications.

Q: Can I use these devices interchangeably in a high-frequency circuit operating at 150 MHz?

A: The ZTX451 and KSD1616AGBU both support 150 MHz or higher transition frequencies and are suitable for high-frequency applications. The KSC1008YBU's 50 MHz transition frequency is insufficient for 150 MHz operation and should not be used in high-frequency circuits.

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