MMBF4391 JFET N-Channel Transistor Equivalent & Substitute Parts

Part Overview

The MMBF4391 is an N-Channel JFET transistor manufactured by onsemi, designed for surface mount applications in the SOT-23-3 package. This device operates at 30 V breakdown voltage with 350 mW maximum power dissipation and is rated for -55°C to 150°C junction temperature operation. The MMBF4391 is classified as obsolete, making identification of active equivalent and substitute parts essential for ongoing design support and procurement continuity.

Key Parameters

Parameter	Value	Unit
FET Type	N-Channel	—
Voltage - Breakdown (V(BR)GSS)	30	V
Current - Drain (Idss) @ Vds (Vgs=0)	50 mA @ 20 V	mA
Voltage - Cutoff (VGS off) @ Id	4 V @ 1 nA	V
Input Capacitance (Ciss) (Max) @ Vds	14 pF @ 20 V	pF
Resistance - RDS(On)	30	Ohms
Power - Max	350	mW
Operating Temperature	-55 to 150	°C (TJ)
Package / Case	SOT-23-3	—
Product Status	Obsolete	—

Substitute Part Grouping Explanation

Substitution of the MMBF4391 is determined by the following critical parameters: N-Channel JFET topology, 30 V breakdown voltage rating, SOT-23-3 surface mount package, and operating temperature range of -55°C to 150°C. Substitute parts must maintain compatibility across these core electrical and mechanical specifications.

The substitute parts are grouped into two categories:

Direct Substitutes (Active Status): Parts that maintain the same 30 V breakdown voltage and SOT-23-3 package while offering active product status and improved availability.

Similar Substitutes (Voltage Variant): Parts that operate at reduced voltage ratings (25 V) but maintain N-Channel JFET topology and SOT-23-3 package compatibility for applications where lower voltage operation is acceptable.

Parameter Comparison

Parameter	MMBF4391	MMBF4392LT1G	CPH3910-TL-E	SMMBF4393LT1G
Manufacturer	onsemi	onsemi	onsemi	onsemi
FET Type	N-Channel	N-Channel	N-Channel	N-Channel
Voltage - Breakdown (V(BR)GSS)	30 V	30 V	25 V	30 V
Drain to Source Voltage (Vdss)	—	30 V	25 V	30 V
Current - Drain (Idss) @ Vds (Vgs=0)	50 mA @ 20 V	25 mA @ 15 V	20 mA @ 5 V	30 mA @ 15 V
Voltage - Cutoff (VGS off) @ Id	4 V @ 1 nA	2 V @ 10 nA	1.8 V @ 100 µA	3 V @ 10 nA
Input Capacitance (Ciss) (Max) @ Vds	14 pF @ 20 V	14 pF @ 15 V	6 pF @ 5 V	14 pF @ 15 V
Resistance - RDS(On)	30 Ohms	60 Ohms	—	100 Ohms
Power - Max	350 mW	225 mW	400 mW	225 mW
Operating Temperature	-55 to 150°C	-55 to 150°C	—	-55 to 150°C
Package / Case	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3
Product Status	Obsolete	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Qualification	—	—	—	AEC-Q101

Engineering Selection Recommendations

MMBF4392LT1G is the primary direct substitute for the MMBF4391. Both devices share identical 30 V breakdown voltage, SOT-23-3 package, and -55°C to 150°C operating temperature range. The MMBF4392LT1G maintains active product status with significantly higher inventory availability (242,300 pcs). This part is suitable for applications where the reduced maximum power rating (225 mW vs. 350 mW) and increased RDS(On) (60 Ohms vs. 30 Ohms) are acceptable within circuit design margins.

SMMBF4393LT1G provides an alternative direct substitute with identical voltage and package specifications. This device carries AEC-Q101 automotive qualification, making it appropriate for automotive and high-reliability applications. The higher RDS(On) value (100 Ohms) requires verification against circuit requirements.

CPH3910-TL-E is a similar substitute suitable only for applications where 25 V operation is acceptable. This part offers the highest maximum power rating (400 mW) among substitutes but operates at reduced voltage and exhibits different electrical characteristics. Use this part only when circuit voltage requirements permit 25 V operation.

All substitute parts maintain ROHS3 compliance and REACH unaffected status, ensuring regulatory compatibility with the original MMBF4391.

Frequently Asked Questions (FAQ)

Q: Can MMBF4392LT1G directly replace MMBF4391 in all applications?

A: MMBF4392LT1G shares the same 30 V breakdown voltage, SOT-23-3 package, and temperature range as MMBF4391. However, the reduced maximum power rating (225 mW vs. 350 mW) and increased RDS(On) (60 Ohms vs. 30 Ohms) require verification against specific circuit power dissipation and on-resistance requirements. Electrical simulation or bench testing is necessary to confirm suitability for your application.

Q: Is SMMBF4393LT1G suitable for automotive applications?

A: SMMBF4393LT1G carries AEC-Q101 automotive qualification, making it appropriate for automotive-grade applications. It maintains 30 V breakdown voltage and SOT-23-3 package compatibility with MMBF4391. The higher RDS(On) value (100 Ohms) must be evaluated against circuit design specifications.

Q: When should CPH3910-TL-E be used as a substitute?

A: CPH3910-TL-E operates at 25 V breakdown voltage, making it suitable only for applications where the circuit voltage requirements do not exceed 25 V. This part offers higher maximum power dissipation (400 mW) but exhibits different drain current and cutoff voltage characteristics. Use this substitute only when voltage derating is acceptable for your design.

Q: Are all substitute parts available in the same package?

A: All substitute parts are available in SOT-23-3 surface mount package, maintaining mechanical compatibility with MMBF4391. Verify supplier device package designations (SOT-23-3 vs. 3-CPH) to ensure PCB footprint compatibility.

Q: What is the impact of different RDS(On) values on circuit performance?

A: RDS(On) directly affects on-state voltage drop and power dissipation. MMBF4391 specifies 30 Ohms, while substitutes range from 60 to 100 Ohms. Higher RDS(On) values increase voltage drop across the device and power dissipation. Verify that circuit design margins accommodate the substitute part's RDS(On) specification.

Q: Do all substitute parts meet the same compliance standards?

A: All substitute parts are ROHS3 compliant and REACH unaffected, matching MMBF4391 regulatory status. SMMBF4393LT1G additionally carries AEC-Q101 automotive qualification. Verify compliance requirements for your specific application before selection.

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