MMBF5434 Equivalent & Substitute Parts

Part Overview

The MMBF5434 is an N-Channel JFET transistor manufactured by onsemi, housed in a SOT-23-3 surface mount package. This device is rated for 25 V breakdown voltage with 30 mA drain current (Idss) at 15 V and 350 mW maximum power dissipation. The part is currently obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity.

Key Parameters

Parameter	Value	Unit
FET Type	N-Channel	—
Voltage - Breakdown (V(BR)GSS)	25	V
Current - Drain (Idss) @ Vds (Vgs=0)	30 mA @ 15 V	mA
Voltage - Cutoff (VGS off) @ Id	1	V @ 3 nA
Input Capacitance (Ciss) (Max) @ Vds	30	pF @ 10V
Power - Max	350	mW
Operating Temperature	-55 to 150	°C
Package / Case	SOT-23-3 (TO-236-3, SC-59)	—
Mounting Type	Surface Mount	—

Substitute Part Grouping Explanation

Substitution for the MMBF5434 is determined by the following criteria:

Direct Substitutes maintain identical or compatible electrical characteristics within the same package:

N-Channel JFET configuration
25 V rated voltage (V(BR)GSS or Vdss)
SOT-23-3 surface mount package
Similar drain current (Idss) and cutoff voltage (VGS off) ranges
Active product status for ongoing availability

Similar Substitutes share the same package and general JFET topology but operate at different voltage or current ratings:

N-Channel JFET configuration
SOT-23-3 surface mount package
Voltage ratings of 25 V or higher
Different Idss or VGS off characteristics
Active product status

The following parts meet direct or similar substitution criteria based on provided electrical and mechanical parameters.

Parameter Comparison

Part Number	Manufacturer	V(BR)GSS / Vdss (V)	Idss @ Vds (mA)	VGS off (V)	Ciss (pF)	Power Max (mW)	Package	Status
MMBF5434	onsemi	25	30 @ 15V	1 @ 3nA	30 @ 10V	350	SOT-23-3	Obsolete
MMBFJ309LT1G	onsemi	25	30	—	—	—	SOT-23-3	Active
MMBFJ310LT1G	onsemi	25	60 @ 10V	—	—	—	SOT-23-3	Active
MMBFJ310LT3G	onsemi	25	60 @ 10V	—	—	—	SOT-23-3	Active
MMBFU310LT1G	onsemi	25	24 @ 10V	2.5 @ 1nA	5 @ 10V	225	SOT-23-3	Active
SMMBFJ310LT1G	onsemi	25	60 @ 10V	—	—	—	SOT-23-3	Active
SMMBFJ310LT3G	onsemi	25	60 @ 10V	—	—	—	SOT-23-3	Active
CPH3910-TL-E	onsemi	25	20 @ 5V	1.8 @ 100µA	6 @ 5V	400	SOT-23-3	Active
MMBF4391LT1G	onsemi	30	50 @ 15V	4 @ 10nA	14 @ 15V	225	SOT-23-3	Active
MMBF4392LT1G	onsemi	30	25 @ 15V	2 @ 10nA	14 @ 15V	225	SOT-23-3	Active
MMBF4393LT1G	onsemi	30	5 @ 15V	0.5 @ 10nA	14 @ 15V	225	SOT-23-3	Active

Engineering Selection Recommendations

Direct Substitutes (Preferred for Obsolete Part Replacement):

MMBFU310LT1G is the primary direct substitute. It maintains 25 V voltage rating, similar drain current characteristics (24 mA @ 10 V versus 30 mA @ 15 V), and identical SOT-23-3 packaging. This part is active and ROHS3 compliant with unlimited moisture sensitivity level.

MMBFJ310LT1G and MMBFJ310LT3G are functionally equivalent with 25 V rating and 60 mA current rating. Both are active products available in standard cut tape or tape & reel packaging. MMBFJ310LT3G is available in higher volume (9,201 pcs).

SMMBFJ310LT1G and SMMBFJ310LT3G are automotive-grade equivalents (AEC-Q101 qualified) with identical electrical specifications to MMBFJ310 variants. These are suitable for applications requiring automotive qualification.

Similar Substitutes (Higher Voltage Rating):

MMBF4391LT1G, MMBF4392LT1G, and MMBF4393LT1G operate at 30 V breakdown voltage with varying drain current characteristics. These parts are suitable when higher voltage margin is required. All three are active, ROHS3 compliant, and available in high volume.

Alternative Substitute (Higher Power Rating):

CPH3910-TL-E provides 400 mW power dissipation (versus 350 mW) with 25 V rating and similar cutoff voltage. This part is active and suitable for applications requiring additional thermal headroom.

All recommended substitutes are manufactured by onsemi, ROHS3 compliant, and rated for -55°C to 150°C operating temperature range.

Frequently Asked Questions (FAQ)

Q: Can MMBFU310LT1G directly replace MMBF5434 in existing designs?

A: Yes. Both devices are N-Channel JFETs with 25 V voltage rating in SOT-23-3 packaging. Drain current specifications are comparable (24 mA @ 10 V versus 30 mA @ 15 V). Verify application-specific requirements for cutoff voltage and input capacitance before implementation.

Q: What is the difference between MMBFJ310LT1G and MMBFJ310LT3G?

A: Both parts are electrically identical N-Channel JFETs with 25 V rating and 60 mA current rating in SOT-23-3 packaging. The difference is packaging format: LT1G is supplied in cut tape with Digi-Reel, while LT3G is supplied in tape & reel. Select based on assembly process requirements.

Q: Are SMMBFJ310 variants suitable for non-automotive applications?

A: Yes. SMMBFJ310LT1G and SMMBFJ310LT3G are automotive-grade (AEC-Q101 qualified) but can be used in general industrial and commercial applications. They maintain identical electrical specifications to standard MMBFJ310 variants.

Q: Why do MMBF4391, MMBF4392, and MMBF4393 have different drain current ratings?

A: These three parts are members of the same JFET family with 30 V voltage rating but different Idss characteristics. MMBF4391 has 50 mA Idss, MMBF4392 has 25 mA Idss, and MMBF4393 has 5 mA Idss. Select based on required drain current for your application.

Q: Is the MMBF5434 obsolete, and what is the recommended replacement?

A: Yes, MMBF5434 is obsolete. MMBFU310LT1G is the recommended direct replacement, offering active product status, identical 25 V voltage rating, comparable drain current, and SOT-23-3 packaging. Alternative direct substitutes include MMBFJ310LT1G and MMBFJ310LT3G.

Q: Can I use a 30 V rated JFET (MMBF4391/4392/4393) in place of the 25 V MMBF5434?

A: Yes, provided your circuit design accommodates the different electrical characteristics. The 30 V parts have higher voltage margin but different Idss and VGS off specifications. Verify circuit performance with the specific part's datasheet parameters before production implementation.

Q: What packaging options are available for substitute parts?

A: All substitute parts use SOT-23-3 (TO-236-3, SC-59) surface mount packaging. Packaging format options include cut tape with Digi-Reel (LT1G variants) and tape & reel (LT3G variants). Select based on your assembly equipment and volume requirements.

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