BF721T1 Equivalent & Substitute Parts

Part Overview

The BF721T1 is a PNP bipolar junction transistor manufactured by onsemi, rated for 300 V collector-emitter breakdown voltage and 50 mA maximum collector current in a surface mount SOT-223 package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The BF721T1 is suitable for low-current switching and amplification applications requiring moderate voltage ratings.

Key Parameters

Parameter	Value
Transistor Type	PNP
Voltage - Collector Emitter Breakdown (Max)	300 V
Current - Collector (Ic) (Max)	50 mA
Power - Max	1.5 W
Frequency - Transition	60 MHz
Package / Case	TO-261-4, TO-261AA (SOT-223)
Mounting Type	Surface Mount
Operating Temperature Range	-65°C to 150°C

Substitute Part Grouping Explanation

Substitution of the BF721T1 is determined by the following electrical and mechanical parameters:

Primary Compatibility Criteria:

Transistor type: PNP configuration
Voltage rating: Minimum 300 V collector-emitter breakdown voltage
Package type: Surface mount SOT-223 (TO-261-4, TO-261AA)
Mounting compatibility: Surface mount technology

Secondary Compatibility Criteria:

Current rating: Equal to or greater than 50 mA maximum collector current
Power dissipation: Equal to or greater than 1.5 W
Operating temperature range: Must encompass or exceed -65°C to 150°C

The substitute parts FZT757TA and FZT957TA meet all primary compatibility criteria and exceed secondary electrical parameters, providing enhanced current handling and power dissipation capabilities while maintaining identical package specifications and voltage ratings.

Parameter Comparison

Parameter	BF721T1 (onsemi)	FZT757TA (Diodes Inc.)	FZT957TA (Diodes Inc.)
Transistor Type	PNP	PNP	PNP
Voltage - Collector Emitter Breakdown (Max)	300 V	300 V	300 V
Current - Collector (Ic) (Max)	50 mA	500 mA	1 A
Vce Saturation (Max)	800 mV @ 5 mA, 30 mA	500 mV @ 10 mA, 100 mA	240 mV @ 300 mA, 1 A
Current - Collector Cutoff (Max)	10 nA	100 nA	50 nA
DC Current Gain (hFE) (Min)	50 @ 25 mA, 20 V	50 @ 100 mA, 5 V	100 @ 500 mA, 10 V
Power - Max	1.5 W	2 W	3 W
Frequency - Transition	60 MHz	30 MHz	85 MHz
Operating Temperature Range	-65°C to 150°C	-55°C to 150°C	-55°C to 150°C
Package / Case	TO-261-4, TO-261AA	TO-261-4, TO-261AA	TO-261-4, TO-261AA
Supplier Device Package	SOT-223	SOT-223-3	SOT-223-3
Product Status	Obsolete	Active	Active
RoHS Status	Non-compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

FZT757TA Selection Criteria: The FZT757TA is suitable for applications where the BF721T1 current rating of 50 mA is insufficient but higher frequency response is not critical. This substitute provides 10× current capacity (500 mA) and increased power dissipation (2 W), with reduced transition frequency (30 MHz versus 60 MHz). The FZT757TA is active product status with ROHS3 compliance, ensuring long-term availability and regulatory alignment.

FZT957TA Selection Criteria: The FZT957TA is suitable for applications requiring maximum current handling (1 A) and highest frequency performance (85 MHz). This substitute provides 20× current capacity and 2× power dissipation compared to the BF721T1. The FZT957TA is active product status with ROHS3 compliance and represents the highest performance option among available substitutes.

Product Status Consideration: Both substitute parts are active products, providing superior long-term availability compared to the obsolete BF721T1. Selection between FZT757TA and FZT957TA depends on application-specific current and frequency requirements rather than availability constraints.

Compliance Consideration: Both substitute parts are ROHS3 compliant, whereas the BF721T1 is non-compliant. Applications subject to RoHS regulations require substitution with either FZT757TA or FZT957TA.

Frequently Asked Questions (FAQ)

Q: Can FZT757TA or FZT957TA be used as direct pin-for-pin replacements for BF721T1?

A: Yes. Both substitute parts share identical package specifications (TO-261-4, TO-261AA, SOT-223 surface mount) and maintain the same pinout configuration as the BF721T1, enabling direct substitution without PCB layout modifications.

Q: What is the primary difference between FZT757TA and FZT957TA?

A: The FZT957TA provides higher maximum collector current (1 A versus 500 mA), higher transition frequency (85 MHz versus 30 MHz), and greater power dissipation capability (3 W versus 2 W). Selection depends on application current and frequency requirements.

Q: Is the operating temperature range difference between BF721T1 (-65°C to 150°C) and the substitutes (-55°C to 150°C) significant?

A: The substitute parts have a narrower lower temperature limit by 10°C. Applications requiring operation below -55°C cannot use FZT757TA or FZT957TA. Applications operating within -55°C to 150°C range are fully compatible.

Q: Why does the BF721T1 have higher transition frequency (60 MHz) than FZT757TA (30 MHz)?

A: Transition frequency is a characteristic of transistor design and manufacturing. The FZT757TA is optimized for higher current handling rather than frequency performance. For applications requiring both high current and high frequency, FZT957TA (85 MHz) is the appropriate selection.

Q: Are there packaging differences between BF721T1 and the substitute parts?

A: All three parts use identical surface mount SOT-223 packages (TO-261-4, TO-261AA). The supplier device package designation differs slightly (SOT-223 versus SOT-223-3), but this reflects manufacturer nomenclature only and does not affect physical compatibility or PCB mounting.

Q: What is the significance of RoHS compliance status?

A: The BF721T1 is RoHS non-compliant, while FZT757TA and FZT957TA are ROHS3 compliant. Applications subject to RoHS regulations (EU Directive 2011/65/EU and amendments) require use of compliant parts. Both substitutes satisfy this requirement.

Q: Can FZT757TA or FZT957TA be used in applications designed for the BF721T1's 50 mA current rating?

A: Yes. Both substitutes exceed the 50 mA requirement and operate safely at lower current levels. The higher current ratings provide design margin and do not create compatibility issues in lower-current applications.

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