1N5366B Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N5366B is a 39 V, 5 W axial through-hole zener diode manufactured by onsemi. This component is classified as obsolete, indicating that direct procurement from the original manufacturer may be limited. The 1N5366B serves as a voltage regulation and protection element in electronic circuits requiring stable 39 V reference voltage with 5 W power dissipation capability. Due to its obsolete status, equivalent and substitute parts from active manufacturers are necessary for new designs and ongoing production requirements.

Key Parameters

Parameter	Value
Voltage - Zener (Nom) (Vz)	39 V
Tolerance	±5%
Power - Max	5 W
Impedance (Max) (Zzt)	14 Ohms
Current - Reverse Leakage @ Vr	500 nA @ 29.7 V
Voltage - Forward (Vf) (Max) @ If	1.2 V @ 1 A
Operating Temperature	-65°C ~ 200°C
Mounting Type	Through Hole
Package / Case	T-18, Axial
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the 1N5366B is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 39 V (nominal)
Voltage tolerance: ±5% or tighter
Power rating: 5 W minimum
Impedance (Zzt): 14 Ohms maximum
Reverse leakage current: 500 nA @ 29.7 V or lower
Forward voltage: 1.2 V @ 1 A or lower
Package type: T-18 Axial through-hole
Mounting: Through-hole configuration

Direct Equivalents are parts that match all primary criteria and maintain identical electrical performance characteristics. These parts are sourced from active manufacturers and provide pin-for-pin, form-factor compatibility.

Similar Substitutes are parts that share the same zener voltage (39 V) and tolerance (±5%) but differ in power rating, package type, or impedance characteristics. These parts are suitable only when circuit design permits reduced power dissipation or alternative package configurations.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (W)	Zzt (Ohms)	Vr Leakage	Vf @ If	Temp Range (°C)	Package	Status
1N5366B	onsemi	39	±5%	5	14	500 nA @ 29.7 V	1.2 V @ 1 A	-65 ~ 200	T-18 Axial	Obsolete
1N5366BG	onsemi	39	±5%	5	14	500 nA @ 29.7 V	1.2 V @ 1 A	-65 ~ 200	T-18 Axial	Active
1N5366B	Microsemi Corporation	39	±5%	5	14	500 nA @ 28.1 V	1.2 V @ 1 A	-65 ~ 150	T-18 Axial	Active
1N5366/TR12	Microchip Technology	39	±20%	5	14	500 nA @ 28.1 V	1.2 V @ 1 A	-65 ~ 150	T-18 Axial	Active
1N5366/TR8	Microchip Technology	39	±20%	5	14	500 nA @ 28.1 V	1.2 V @ 1 A	-65 ~ 150	T-18 Axial	Active
1N5366A/TR12	Microchip Technology	39	±10%	5	14	500 nA @ 28.1 V	1.2 V @ 1 A	-65 ~ 150	T-18 Axial	Active
1N5366A/TR8	Microchip Technology	39	±10%	5	14	500 nA @ 28.1 V	1.2 V @ 1 A	-65 ~ 150	T-18 Axial	Active
1N5259B	Microchip Technology	39	±5%	0.5	80	100 nA @ 30 V	1.5 V @ 200 mA	-65 ~ 175	DO-35 Axial	Active
1N4123-1	Microchip Technology	39	±5%	0.5	200	10 nA @ 29.7 V	1.1 V @ 200 mA	-65 ~ 175	DO-35 Axial	Active

Engineering Selection Recommendations

Direct Equivalent (Recommended Primary Choice):

The 1N5366BG (onsemi, Active status) is the direct equivalent to the obsolete 1N5366B. This part maintains identical electrical specifications including 39 V nominal zener voltage, ±5% tolerance, 5 W power rating, 14 Ohms impedance, and T-18 axial package configuration. The 1N5366BG is currently in active production status with 4,100 pieces in stock, ensuring supply continuity. The primary difference is packaging format (Bulk versus unspecified for the original), which does not affect electrical performance or circuit compatibility.

Alternative Equivalent (Secondary Choice):

The 1N5366B from Microsemi Corporation (Active status) provides electrical equivalence with identical zener voltage, tolerance, power rating, and impedance specifications. This part operates within a reduced temperature range (-65°C to 150°C versus -65°C to 200°C for the onsemi original), which is acceptable for most industrial and commercial applications. Microsemi's 1N5366B is actively produced with 5,200 pieces in stock.

Acceptable Substitutes with Tolerance Variance:

The 1N5366A/TR12 and 1N5366A/TR8 (Microchip Technology, Active status) provide 39 V zener voltage with ±10% tolerance and identical 5 W power rating. These parts are suitable for applications where ±10% voltage tolerance is acceptable. Both are supplied in tape and reel packaging and are actively produced.

The 1N5366/TR12 and 1N5366/TR8 (Microchip Technology, Active status) provide 39 V zener voltage with ±20% tolerance and 5 W power rating. These parts are suitable only for applications with relaxed voltage tolerance requirements. Both are actively produced in tape and reel format.

Lower Power Alternatives (Limited Substitution):

The 1N5259B (Microchip Technology, Active status) and 1N4123-1 (Microchip Technology, Active status) share the 39 V zener voltage specification but are rated for 500 mW power dissipation. These parts are suitable only for low-power applications where the 5 W rating of the original is not required. Both use DO-35 package format, which differs from the T-18 axial package of the 1N5366B.

Compliance Considerations:

The original 1N5366B (onsemi) is RoHS non-compliant. The 1N5366BG (onsemi) is ROHS3 compliant, providing environmental compliance advantage for new designs. All Microchip Technology alternatives listed are RoHS non-compliant. All parts listed maintain REACH Unaffected status and EAR99 export classification.

Frequently Asked Questions (FAQ)

Q: Can the 1N5366BG directly replace the obsolete 1N5366B?

A: Yes. The 1N5366BG is a direct electrical and mechanical equivalent. Both parts share identical zener voltage (39 V), tolerance (±5%), power rating (5 W), impedance (14 Ohms), and T-18 axial package configuration. The 1N5366BG is currently in active production, making it the recommended replacement for the obsolete 1N5366B.

Q: What is the difference between 1N5366A and 1N5366B?

A: The primary difference is voltage tolerance. The 1N5366A has ±10% tolerance, while the 1N5366B has ±5% tolerance. Both share identical 39 V nominal zener voltage, 5 W power rating, and T-18 axial package. The 1N5366B provides tighter voltage regulation suitable for applications requiring more precise voltage reference.

Q: Can I use 1N5259B or 1N4123-1 as replacements for the 1N5366B?

A: These parts are not direct replacements. While they share the 39 V zener voltage specification, they are rated for only 500 mW power dissipation compared to the 5 W rating of the 1N5366B. Additionally, they use DO-35 package format instead of T-18 axial. These parts are suitable only for low-power applications where the original 5 W rating is not required and where package format change is acceptable.

Q: What does the ±5% tolerance specification mean?

A: The ±5% tolerance indicates that the actual zener voltage will fall within a range of 39 V ± 1.95 V (37.05 V to 40.95 V). This specification is critical for voltage regulation applications. Parts with ±10% or ±20% tolerance have wider voltage ranges and are suitable only for applications with relaxed voltage regulation requirements.

Q: Are all substitute parts available in the same package format?

A: No. The 1N5366B, 1N5366BG, and Microchip 1N5366 variants are all supplied in T-18 axial package format, maintaining mechanical compatibility. However, the 1N5259B and 1N4123-1 use DO-35 package format, which differs in physical dimensions and pin spacing. Package format change requires circuit board layout modification.

Q: What is the significance of the "Active" versus "Obsolete" product status?

A: Active status indicates the part is currently in production and available from the manufacturer. Obsolete status indicates the manufacturer has discontinued production. The 1N5366B (onsemi) is obsolete, making it difficult to procure for new designs. Active alternatives ensure long-term supply availability and design continuity.

Q: Does RoHS compliance affect electrical performance?

A: RoHS compliance does not affect electrical performance. RoHS compliance indicates the part does not contain restricted hazardous substances (lead, cadmium, mercury, etc.). The 1N5366BG is ROHS3 compliant, providing environmental and regulatory advantage for new designs, while maintaining identical electrical specifications to the non-compliant original 1N5366B.

Q: What is the difference between tape and reel (TR) packaging and bulk packaging?

A: Tape and reel packaging is used for automated assembly processes, where components are supplied on continuous tape in reels. Bulk packaging is used for manual assembly or smaller quantity orders. Both packaging formats contain identical components with identical electrical specifications. Packaging format selection depends on manufacturing process requirements, not electrical performance.

Q: Can I use parts with different operating temperature ranges?

A: Operating temperature range substitution depends on application requirements. The original 1N5366B operates from -65°C to 200°C. The Microsemi 1N5366B operates from -65°C to 150°C, which is acceptable for most industrial and commercial applications but may not be suitable for high-temperature environments exceeding 150°C. Verify application temperature requirements before selecting a substitute with a reduced temperature range.

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