NZT651 Equivalent & Substitute Parts

Part Overview

The NZT651 is an NPN bipolar junction transistor manufactured by onsemi, rated for 60V collector-emitter breakdown voltage and 4A maximum collector current in a surface mount SOT-223-4 package. This device is classified as obsolete, necessitating identification of equivalent and substitute components for ongoing design requirements and production continuity. The NZT651 operates across a temperature range of -55°C to 150°C and delivers 1.2W maximum power dissipation with a transition frequency of 75MHz.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	60	V
Current - Collector (Ic) (Max)	4	A
Power - Max	1.2	W
Frequency - Transition	75	MHz
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	TO-261-4, TO-261AA	—
Vce Saturation (Max)	500mV @ 200mA, 2A	—
DC Current Gain (hFE) (Min)	40 @ 2A, 2V	—
Current - Collector Cutoff (Max)	100	nA
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the NZT651 is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Transistor Type: NPN configuration required
Voltage - Collector Emitter Breakdown: Minimum 60V (equal or greater)
Current - Collector (Ic) (Max): Minimum 4A (equal or greater)
Power - Max: Minimum 1.2W (equal or greater)
Mounting Type: Surface Mount
Package / Case: TO-261-4 or TO-261AA compatible
Operating Temperature: Must support -55°C to 150°C range or equivalent maximum rating

Secondary Compatibility Parameters:

Vce Saturation characteristics
DC Current Gain (hFE)
Current - Collector Cutoff (ICBO)
RoHS and MSL compliance

Substitute parts are grouped into two categories:

Category 1 - Manufacturer Recommended (Active Status): PZT651T1G meets voltage and package requirements but operates at reduced maximum collector current (2A) and power dissipation (800mW). This part is suitable for applications where the full 4A rating is not required.

Category 2 - Similar Electrical Characteristics (Active Status): Parts including FZT651TC, FZT651TA, FZT851TA, BCP55, BCP55TA, 2STN1550, and BSP41,115 provide equivalent or superior electrical performance within the 60V voltage class and SOT-223 package family. These parts vary in maximum collector current ratings, power dissipation, and transition frequency.

Parameter Comparison

Part Number	Manufacturer	Product Status	Ic (Max) [A]	Vce Breakdown (Max) [V]	Power (Max) [W]	Frequency [MHz]	Temp Range [°C]	Package
NZT651	onsemi	Obsolete	4	60	1.2	75	-55 to 150	SOT-223-4
PZT651T1G	onsemi	Active	2	60	0.8	75	-55 to 150	SOT-223
BCP55	onsemi	Active	1.5	60	1.5	—	-55 to 150	SOT-223-4
2STN1550	STMicroelectronics	Active	5	50	1.6	—	-55 to 150	SOT-223
BCP55TA	Diodes Incorporated	Active	1	60	2	150	-55 to 150	SOT-223-3
BSP41,115	Nexperia USA Inc.	Active	1	60	1.3	100	-55 to 150	SOT-223
FZT491TA	Diodes Incorporated	Active	1	60	2	150	-55 to 150	SOT-223-3
FZT651TA	Diodes Incorporated	Active	3	60	2	175	-55 to 150	SOT-223-3
FZT651TC	Diodes Incorporated	Active	3	60	2	175	-55 to 150	SOT-223-3
FZT851TA	Diodes Incorporated	Active	6	60	3	130	-55 to 150	SOT-223-3

Engineering Selection Recommendations

For Direct Replacement (Equivalent Current Rating):

FZT651TC and FZT651TA from Diodes Incorporated provide the closest electrical equivalence to the NZT651 within the active product portfolio. Both devices maintain the 60V collector-emitter breakdown voltage, deliver 3A maximum collector current (within 75% of the original 4A specification), and operate across the full -55°C to 150°C temperature range. These parts are ROHS3 compliant and carry MSL 1 rating. FZT651TC is supplied in Tape & Reel packaging, while FZT651TA is available in Cut Tape format.

For Higher Current Applications:

FZT851TA from Diodes Incorporated extends the maximum collector current to 6A while maintaining 60V voltage rating and full temperature range operation. This device provides superior current handling capability and increased power dissipation (3W) compared to the NZT651.

For Reduced Current Applications:

PZT651T1G from onsemi, the manufacturer-recommended substitute, operates at 2A maximum collector current with identical 60V voltage rating and 75MHz transition frequency. This part is suitable for applications where the full 4A rating is not required and offers the advantage of being from the original manufacturer.

For Automotive Applications:

BSP41,115 from Nexperia USA Inc. is qualified to AEC-Q100 automotive standards and operates at 1A maximum collector current with 60V voltage rating. This part is appropriate for automotive-grade designs requiring equivalent substitution.

Voltage Consideration:

2STN1550 from STMicroelectronics operates at 50V collector-emitter breakdown voltage (10V lower than the NZT651) with 5A maximum collector current. This part is suitable only for applications where the reduced voltage rating is acceptable.

All recommended substitute parts maintain ROHS3 compliance and MSL 1 moisture sensitivity rating consistent with the original NZT651 specification.

Frequently Asked Questions (FAQ)

Q: Can the PZT651T1G directly replace the NZT651 in all applications?

A: The PZT651T1G is the manufacturer-recommended substitute from onsemi but operates at 2A maximum collector current compared to the NZT651's 4A rating. Direct replacement is appropriate only for applications where the circuit design does not require the full 4A current capability. Verify circuit current requirements before substitution.

Q: What is the primary difference between FZT651TC and FZT651TA?

A: Both parts are electrically identical with 3A maximum collector current, 60V voltage rating, and 175MHz transition frequency. The difference is packaging: FZT651TC is supplied in Tape & Reel format, while FZT651TA is supplied in Cut Tape format. Select based on procurement and assembly requirements.

Q: Is the 2STN1550 a suitable substitute despite the 50V voltage rating?

A: The 2STN1550 operates at 50V collector-emitter breakdown voltage, which is 10V lower than the NZT651's 60V rating. This part is suitable only for applications where the circuit design operates below 50V. Do not use this part in circuits designed for the full 60V rating.

Q: Why does the BCP55 have a lower maximum collector current than the NZT651?

A: The BCP55 is rated for 1.5A maximum collector current compared to the NZT651's 4A. This part is suitable for lower-current applications. For applications requiring 4A or higher current capability, select FZT651TC, FZT651TA, or FZT851TA instead.

Q: Are all substitute parts ROHS3 compliant?

A: Yes, all substitute parts listed in this reference are ROHS3 compliant and carry MSL 1 (Unlimited) moisture sensitivity rating, consistent with the original NZT651 specification.

Q: What is the significance of the SOT-223-3 versus SOT-223-4 package designation?

A: Both designations refer to the same physical SOT-223 package family with TO-261-4 or TO-261AA case compatibility. The numeric suffix indicates the number of leads. All parts listed are compatible with the original NZT651 mounting footprint.

Q: Which substitute part offers the highest current capability?

A: The FZT851TA from Diodes Incorporated provides the highest maximum collector current at 6A, along with 3W power dissipation and 130MHz transition frequency, all within the 60V voltage class and full -55°C to 150°C operating temperature range.

Q: Can the BSP41,115 be used in non-automotive applications?

A: Yes, the BSP41,115 is qualified to AEC-Q100 automotive standards but can be used in non-automotive applications. Its 1A maximum collector current and 60V voltage rating make it suitable for lower-current circuit designs requiring automotive-grade reliability.

Q: What should be verified before selecting a substitute part?

A: Verify the following circuit requirements: (1) maximum collector current needed, (2) collector-emitter voltage rating required, (3) power dissipation capability, (4) operating temperature range, (5) transition frequency requirements, and (6) packaging format (Tape & Reel or Cut Tape). Compare these requirements against the substitute part specifications provided in the Parameter Comparison table.

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