FDH333_T50R Equivalent & Substitute Parts

Part Overview

The FDH333_T50R is a general-purpose rectifier diode manufactured by onsemi, rated for 125 V DC reverse voltage and 200 mA average rectified current in a DO-35 through-hole package. This component is classified as obsolete, indicating discontinued production and limited availability through standard distribution channels. Identification of equivalent and substitute parts is necessary to support ongoing maintenance, repair, and legacy system support where this diode remains in active service.

Substiute Parts

FDH333_T50R

onsemiIn Stock: 815FDH333_T50R Datasheet

Current PartRFQ

FDH333

Fairchild SemiconductorIn Stock: 3614FDH333 Datasheet

DirectRFQ

1N4448

Microchip TechnologyIn Stock: 502361N4448 Datasheet

SimilarRFQ

FDH333TR

onsemiIn Stock: 168643FDH333TR Datasheet

Parametric EquivalentRFQ

BAY135-TAP

Vishay General Semiconductor - Diodes DivisionIn Stock: 6147BAY135-TAP Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the FDH333_T50R are classified into two categories based on electrical parameter alignment:

Direct Equivalent (Parametric Match): Parts that maintain identical or superior electrical specifications across all critical parameters: 125 V reverse voltage rating, 200 mA average rectified current, small signal speed classification, and DO-35 through-hole package configuration. These parts satisfy direct functional replacement without circuit redesign.

Similar Equivalent (Voltage Derating Required): Parts that match current rating and package type but operate at reduced reverse voltage ratings. These parts require circuit analysis to confirm voltage margin adequacy in the target application.

The following parameters determine substitution eligibility:

• Voltage - DC Reverse (Vr) (Max): Must equal or exceed 125 V for direct equivalence
• Current - Average Rectified (Io): Must equal or exceed 200 mA
• Mounting Type: Must be Through Hole
• Package / Case: Must be DO-35 or DO-204AH compatible
• Speed Classification: Must support Small Signal ≤ 200mA operation

Parameter Comparison

Engineering Selection Recommendations

Primary Recommendation: FDH333TR (onsemi)

The FDH333TR is the preferred substitute for the FDH333_T50R. This part maintains identical electrical specifications across all critical parameters: 125 V reverse voltage, 200 mA average rectified current, 1.15 V forward voltage at 300 mA, and 3 nA reverse leakage at 125 V. The FDH333TR is currently in active production status with 168,620 units in stock, ensuring long-term availability. The part carries ROHS3 compliance certification, meeting modern regulatory requirements. The only difference is packaging format (Cut Tape versus bulk), which does not affect electrical performance or functional compatibility.

Secondary Recommendation: BAY135-TAP (Vishay General Semiconductor)

The BAY135-TAP provides full parametric equivalence with 125 V reverse voltage and 200 mA current rating. This part is actively produced and ROHS3 compliant. Forward voltage specification (1 V @ 30 mA) is superior to the main part. Reverse leakage is specified at 60 V rather than 125 V, but the 3 nA value at this reduced voltage indicates acceptable leakage characteristics. Capacitance is marginally lower at 5 pF. This part is supplied in Tape & Box packaging with 6,090 units available.

Alternative Consideration: FDH333 (Fairchild Semiconductor)

The FDH333 from Fairchild Semiconductor matches all electrical specifications of the main part exactly. However, this part is classified as obsolete with RoHS non-compliant status. Selection of this part is appropriate only when legacy compliance requirements or specific circuit validation history necessitate the exact original part number.

Not Recommended: 1N4448 (Microchip Technology)

The 1N4448 operates at a maximum reverse voltage of 75 V, which is 50 V below the FDH333_T50R specification. This voltage derating introduces circuit margin reduction and is suitable only for applications where the actual operating voltage is confirmed to remain below 75 V. The part is discontinued at DiGi Electronics and carries RoHS non-compliant status.

Frequently Asked Questions (FAQ)

Q: Can the FDH333TR directly replace the FDH333_T50R without circuit modification?

A: Yes. The FDH333TR maintains identical electrical specifications for voltage rating, current capacity, forward voltage, reverse leakage, and capacitance. The only difference is packaging format (Cut Tape versus bulk), which does not affect electrical performance. Direct substitution is supported.

Q: What is the significance of the 125 V reverse voltage rating?

A: The 125 V rating establishes the maximum reverse bias voltage the diode can withstand without breakdown. Substitute parts must maintain this rating or higher to preserve circuit safety margins. The 1N4448 at 75 V does not meet this requirement for direct substitution.

Q: Why is the FDH333TR preferred over the FDH333 despite identical specifications?

A: The FDH333TR is in active production with 168,620 units in stock, while the FDH333 is obsolete. The FDH333TR carries ROHS3 compliance, meeting current regulatory standards. For new designs and ongoing support, the FDH333TR ensures long-term availability and compliance.

Q: Does packaging format affect electrical performance?

A: No. The FDH333_T50R (bulk packaging) and FDH333TR (Cut Tape packaging) are electrically identical. Packaging format affects only handling, storage, and assembly processes. Both parts are compatible with through-hole soldering and axial lead mounting.

Q: Can the BAY135-TAP be used in applications requiring the exact forward voltage specification?

A: The BAY135-TAP forward voltage is specified at 1 V @ 30 mA, compared to 1.15 V @ 300 mA for the FDH333_T50R. These measurements are taken at different current levels, making direct comparison inappropriate. The BAY135-TAP exhibits lower forward voltage at lower current, which is typical diode behavior. Circuit validation is required to confirm compatibility with specific voltage drop requirements.

Q: What does "Small Signal ≤ 200mA (Io), Any Speed" classification mean?

A: This classification indicates the diode is optimized for applications with average rectified current not exceeding 200 mA and supports any switching speed category. All substitute parts maintain this classification, confirming compatibility with the original application current range.

Q: Is the 1N4448 suitable for applications operating below 75 V?

A: The 1N4448 is electrically functional at voltages below 75 V. However, this part is discontinued at DiGi Electronics and carries RoHS non-compliant status. The FDH333TR or BAY135-TAP are preferred alternatives even for reduced-voltage applications due to active production status and regulatory compliance.

Q: What is ROHS3 compliance and why does it matter?

A: ROHS3 compliance indicates the part meets Restriction of Hazardous Substances Directive requirements, restricting lead, cadmium, mercury, and other hazardous materials. This certification is required for products sold in the European Union and increasingly demanded by global customers. The FDH333TR and BAY135-TAP carry this certification; the FDH333 and 1N4448 do not.

Q: Are there inventory considerations when selecting a substitute?

A: Yes. The FDH333TR has 168,620 units in stock, providing substantial availability. The BAY135-TAP has 6,090 units available. The FDH333 (Fairchild) has 3,524 units, and the 1N4448 has 50,170 units. For long-term production support, the FDH333TR is the most secure choice.