FDH300 Equivalent & Substitute Parts

Part Overview

The FDH300 is a general-purpose rectifier diode 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, which necessitates identification of active equivalent and substitute parts for ongoing design and procurement requirements. Equivalent parts maintain identical or superior electrical specifications, while substitute parts provide functional alternatives within acceptable parameter ranges for general-purpose rectification applications.

Key Parameters

Parameter	Value	Unit
Voltage - DC Reverse (Vr) (Max)	125	V
Current - Average Rectified (Io)	200	mA
Voltage - Forward (Vf) (Max) @ If	1	V @ 200 mA
Current - Reverse Leakage @ Vr	1	nA @ 125 V
Capacitance @ Vr, F	6	pF @ 0V, 1MHz
Mounting Type	Through Hole	-
Package / Case	DO-204AH, DO-35, Axial	-
Operating Temperature - Junction (Max)	175	°C
Technology	Standard	-
Speed Classification	Small Signal ≤ 200mA (Io), Any Speed	-

Substitute Part Grouping Explanation

Substitution of the FDH300 is determined by the following critical parameters: reverse voltage rating (Vr), average rectified current (Io), forward voltage drop (Vf), reverse leakage current, and physical package compatibility. All substitute parts must maintain through-hole DO-35 package configuration and operate within the small-signal rectification category.

Direct Equivalents possess identical electrical specifications across all critical parameters, including 125 V reverse voltage and 200 mA current rating.

Parametric Equivalents maintain the same reverse voltage and current ratings but may exhibit minor variations in secondary characteristics such as capacitance or leakage current within acceptable engineering tolerances.

Similar Alternatives provide functional rectification capability but with modified voltage or current ratings. These parts are suitable only when circuit design permits operation at the specified alternative ratings without performance degradation.

Parameter Comparison

Part Number	Manufacturer	Vr (Max) [V]	Io [mA]	Vf (Max) @ If [V]	Reverse Leakage @ Vr [nA]	Capacitance @ Vr [pF]	Product Status	Package
FDH300	onsemi	125	200	1 @ 200 mA	1 @ 125 V	6 @ 0V, 1MHz	Obsolete	DO-35
FDH300A	onsemi	125	200	1 @ 200 mA	1 @ 125 V	6 @ 0V, 1MHz	Active	DO-35
FDH300A_NL	Fairchild Semiconductor	125	200	1 @ 200 mA	1 @ 125 V	6 @ 0V, 1MHz	Active	DO-35
FDH3595	onsemi	125	200	1 @ 200 mA	1 @ 125 V	8 @ 0V, 1MHz	Active	DO-35
1N458	Microchip Technology	150	150	1 @ 100 mA	1000 @ 150 V	-	Active	DO-35
1N4448	Microchip Technology	75	200	1 @ 100 mA	25 @ 20 V	-	Discontinued at DiGi Electronics	DO-35

Engineering Selection Recommendations

Primary Substitutes (Direct Equivalents):

FDH300A and FDH300A_NL are direct electrical equivalents to the obsolete FDH300, maintaining identical reverse voltage (125 V), average rectified current (200 mA), forward voltage drop (1 V @ 200 mA), and reverse leakage current (1 nA @ 125 V) specifications. Both parts are in active production status. FDH300A is supplied by onsemi with RoHS3 compliance. FDH300A_NL is supplied by Fairchild Semiconductor. Selection between these parts depends on supply chain availability and procurement requirements.

Secondary Equivalent (Parametric):

FDH3595 from onsemi maintains identical voltage and current ratings with a minor capacitance variation (8 pF versus 6 pF at 0V, 1MHz). This part is active and RoHS3 compliant. The capacitance difference is negligible for general-purpose rectification applications and does not affect functional compatibility.

Alternative Substitutes (Limited Compatibility):

1N458 (Microchip Technology) provides higher reverse voltage capability (150 V) but reduced average rectified current (150 mA). This part is suitable only in applications where the 150 mA current rating is acceptable and the higher voltage rating provides design margin.

1N4448 (Microchip Technology) maintains the 200 mA current rating but operates at reduced reverse voltage (75 V). This part is discontinued at DiGi Electronics and is suitable only in applications where 75 V reverse voltage is sufficient. Higher reverse leakage current (25 nA @ 20 V) compared to the FDH300 specification must be evaluated for circuit performance.

Frequently Asked Questions (FAQ)

Q: Can FDH300A be used as a direct replacement for FDH300?

A: Yes. FDH300A is a direct electrical equivalent with identical reverse voltage (125 V), average rectified current (200 mA), forward voltage drop (1 V @ 200 mA), and reverse leakage current (1 nA @ 125 V) specifications. FDH300A is in active production status, whereas FDH300 is obsolete.

Q: What is the difference between FDH300A and FDH300A_NL?

A: Both parts are direct electrical equivalents with identical electrical specifications. FDH300A is manufactured by onsemi and is RoHS3 compliant. FDH300A_NL is manufactured by Fairchild Semiconductor. Selection depends on supply chain availability and procurement preferences.

Q: Is FDH3595 compatible with FDH300 applications?

A: Yes. FDH3595 maintains identical reverse voltage (125 V) and average rectified current (200 mA) ratings. The capacitance specification differs slightly (8 pF versus 6 pF at 0V, 1MHz), which does not affect functional compatibility in general-purpose rectification circuits.

Q: Can 1N458 replace FDH300?

A: 1N458 is a functional alternative only in applications where the reduced average rectified current (150 mA versus 200 mA) is acceptable. The higher reverse voltage rating (150 V) provides additional design margin but does not enable direct substitution in all applications.

Q: Can 1N4448 replace FDH300?

A: 1N4448 is a functional alternative only in applications where the reduced reverse voltage rating (75 V versus 125 V) is acceptable. This part is discontinued at DiGi Electronics and exhibits higher reverse leakage current (25 nA @ 20 V) compared to FDH300 specifications.

Q: Are all substitute parts available in DO-35 through-hole package?

A: Yes. All listed substitute parts are supplied in DO-35 through-hole package configuration, maintaining physical and mechanical compatibility with FDH300 circuit board layouts.

Q: What compliance certifications apply to substitute parts?

A: FDH300A and FDH3595 are RoHS3 compliant. FDH300A_NL compliance status is not applicable per Fairchild Semiconductor specifications. All parts maintain REACH unaffected status and EAR99 export classification.

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