SF18-AP Equivalent & Substitute Parts

Part Overview

The SF18-AP is a general-purpose rectifier diode rated for 600 V DC reverse voltage and 1 A average rectified current in a through-hole DO-41 package. This component is classified as obsolete, which necessitates identification of active equivalent and substitute parts for ongoing design requirements and procurement needs. The SF18-AP belongs to the fast recovery diode category with a reverse recovery time of 35 nanoseconds, suitable for standard rectification applications requiring moderate switching speeds.

Substiute Parts

SF18-AP

Micro Commercial CoIn Stock: 1043SF18-AP Datasheet

Current PartRFQ

SF18G-AP

Micro Commercial CoIn Stock: 920SF18G-AP Datasheet

DirectRFQ

1N4937E-E3/53

Vishay General Semiconductor - Diodes DivisionIn Stock: 11371N4937E-E3/53 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the SF18-AP is determined by strict equivalence in the following electrical and mechanical parameters:

Critical Matching Parameters:

• Voltage - DC Reverse (Vr) (Max): 600 V
• Current - Average Rectified (Io): 1 A
• Mounting Type: Through Hole
• Package / Case: DO-204AL, DO-41, Axial

Secondary Compatibility Parameters:

• Reverse Recovery Time (trr): ≤ 500 ns (Fast Recovery classification)
• Current - Reverse Leakage @ Vr: ≤ 5 µA @ 600 V
• Operating Temperature Range: Minimum -55°C to maximum ≥ 125°C
• RoHS3 Compliance: Required

Substitute parts must satisfy all critical matching parameters. Variations in forward voltage, reverse recovery time within the fast recovery specification, and extended temperature ranges are permissible. Parts with active product status are preferred for new designs.

Parameter Comparison

Engineering Selection Recommendations

SF18G-AP (Direct Substitute - Preferred)

The SF18G-AP is the direct equivalent from the same manufacturer (Micro Commercial Co) with identical electrical ratings and package specifications. This part holds active product status, ensuring long-term availability and supply chain continuity. The SF18G-AP demonstrates improved forward voltage characteristics (1.3 V versus 1.7 V at 1 A), resulting in lower power dissipation. Extended operating temperature range (-55°C to 150°C) provides additional thermal margin. ROHS3 compliance and unlimited moisture sensitivity level (MSL 1) match the original specification. This part is the primary choice for direct replacement in existing designs.

1N4937E-E3/53 (Similar Substitute - Alternative)

The 1N4937E-E3/53 from Vishay General Semiconductor - Diodes Division satisfies all critical electrical and mechanical parameters with active product status. This part exhibits superior forward voltage performance (1.2 V at 1 A) and lower junction capacitance (12 pF versus 25 pF), beneficial for high-frequency applications. The reverse recovery time of 200 nanoseconds remains within the fast recovery classification (≤ 500 ns) specified for this product category. Extended operating temperature range (-55°C to 150°C) and ROHS3 compliance ensure regulatory alignment. This part serves as a qualified alternative when SF18G-AP availability is constrained.

Both substitute parts maintain electrical equivalence within the 600 V / 1 A rectifier diode classification and are suitable for direct circuit substitution without design modification.

Frequently Asked Questions (FAQ)

Q: Can the SF18G-AP directly replace the SF18-AP without circuit modification?

A: Yes. The SF18G-AP maintains identical voltage and current ratings (600 V, 1 A), matching package configuration (DO-41), and equivalent reverse recovery time (35 ns). The improved forward voltage characteristic (1.3 V versus 1.7 V) reduces power dissipation without affecting circuit functionality. No design changes are required.

Q: What is the difference between the SF18G-AP and 1N4937E-E3/53?

A: Both parts meet the 600 V / 1 A specification and through-hole DO-41 package requirement. The primary difference is reverse recovery time: SF18G-AP operates at 35 ns while 1N4937E-E3/53 operates at 200 ns. Both remain classified as fast recovery diodes (≤ 500 ns). The 1N4937E-E3/53 exhibits lower forward voltage (1.2 V) and capacitance (12 pF), making it suitable for applications prioritizing switching efficiency. Selection depends on specific circuit switching frequency requirements.

Q: Why is the SF18-AP listed as obsolete?

A: Obsolete status indicates the manufacturer has discontinued production. The SF18G-AP provides an active equivalent from the same manufacturer, ensuring continued availability and supply chain support for applications requiring this rectifier specification.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. The SF18G-AP and 1N4937E-E3/53 both carry ROHS3 compliance certification, matching the original SF18-AP specification. Both parts are suitable for applications requiring RoHS3 regulatory compliance.

Q: Can the 1N4937E-E3/53 be used in high-temperature applications?

A: Yes. The 1N4937E-E3/53 supports an operating junction temperature range of -55°C to 150°C, providing 25°C additional thermal margin compared to the SF18-AP (-55°C to 125°C). This extended range accommodates applications with elevated ambient or self-heating conditions.

Q: What is the significance of the DO-41 package designation?

A: DO-41 is an axial through-hole package for discrete diodes. All three parts (SF18-AP, SF18G-AP, and 1N4937E-E3/53) utilize this standardized package, ensuring mechanical and electrical compatibility with existing printed circuit board layouts and assembly processes.

Q: How does forward voltage affect circuit performance?

A: Forward voltage determines power dissipation during conduction. The SF18G-AP (1.3 V) and 1N4937E-E3/53 (1.2 V) dissipate less power than the SF18-AP (1.7 V) at 1 A, reducing thermal load. In low-power applications, this difference is negligible; in high-duty-cycle circuits, improved efficiency may justify part selection based on forward voltage characteristics.