TF408-3-TL-H JFET N-Channel Equivalent & Substitute Parts

Part Overview

The TF408-3-TL-H is an N-Channel JFET transistor manufactured by onsemi, designed for low-power surface mount applications. This device features a maximum drain current of 10 mA and operates at a maximum junction temperature of 150°C. The part is classified as obsolete, necessitating identification of active equivalent components for new designs and ongoing production requirements.

Substiute Parts

TF408-3-TL-H

onsemiIn Stock: 918TF408-3-TL-H Datasheet

Current PartRFQ

TF412ST5G

onsemiIn Stock: 75795TF412ST5G Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the TF408-3-TL-H is determined by the following critical electrical and mechanical parameters:

• FET Channel Type: N-Channel configuration must be maintained
• Maximum Drain Current (Id): Substitute must support minimum 10 mA
• Drain-Source Voltage (Vdss): Substitute must meet or exceed application voltage requirements
• Gate-Source Cutoff Voltage (VGS off): Must remain within 180 mV @ 1 µA specification
• Input Capacitance (Ciss): Must not exceed 4 pF @ 10 V
• Maximum Power Dissipation: Substitute must support minimum 30 mW
• Operating Temperature Range: Must support 150°C junction temperature
• Mounting Type: Surface mount configuration required
• Drain Current (Idss): Must match 1.2 mA @ 10 V specification

The TF412ST5G meets all these criteria while offering enhanced voltage ratings and increased power handling capability.

Parameter Comparison

Engineering Selection Recommendations

The TF412ST5G is the qualified substitute for the TF408-3-TL-H based on the following factors:

Electrical Compatibility: The TF412ST5G maintains identical drain current specifications (10 mA maximum), gate-source cutoff voltage (180 mV @ 1 µA), and input capacitance (4 pF @ 10 V). These parameters ensure functional equivalence in existing circuit designs.

Enhanced Ratings: The substitute provides increased drain-source voltage rating (30 V) and higher power dissipation capability (100 mW versus 30 mW), offering improved design margin and reliability in applications where the original part's specifications are marginal.

Product Status and Compliance: The TF412ST5G is an active product with ROHS3 compliance certification, ensuring long-term availability and regulatory alignment. The obsolete status of the TF408-3-TL-H makes transition to the active substitute necessary for production continuity.

Packaging Consideration: Package differences exist between the two devices (3-USFP versus SOT-883 XDFN3). PCB layout modifications are required for physical implementation.

Frequently Asked Questions (FAQ)

Q: Can the TF412ST5G directly replace the TF408-3-TL-H without circuit modifications?

A: Electrical parameters are compatible for direct functional substitution. However, the package change from 3-USFP to SOT-883 (XDFN3) requires PCB layout redesign. Verify that the 30 V Vdss and 100 mW power rating do not create design conflicts in your application.

Q: What are the key electrical parameters that define substitution eligibility?

A: Substitution is determined by matching drain current (10 mA), gate-source cutoff voltage (180 mV @ 1 µA), input capacitance (4 pF @ 10 V), and N-Channel configuration. The TF412ST5G meets all these criteria.

Q: Why does the TF412ST5G have higher power and voltage ratings?

A: The TF412ST5G is a more recent design offering enhanced specifications. Higher ratings provide additional design margin and do not prevent use in applications designed for the lower-rated TF408-3-TL-H.

Q: Are there compliance or supply chain advantages to using the TF412ST5G?

A: Yes. The TF412ST5G is an active product with ROHS3 compliance and significantly higher inventory availability (75,755 units in stock versus 887 units for the obsolete TF408-3-TL-H). This ensures long-term supply security and regulatory compliance.

Q: What package considerations apply to this substitution?

A: The TF408-3-TL-H uses a 3-SMD flat lead package, while the TF412ST5G uses SOT-883 (XDFN3) with dimensions 1x0.6 mm. Footprint redesign is mandatory. Consult device datasheets for exact pin configuration and placement requirements.