BZX79C33 Equivalent & Substitute Parts

Part Overview

The BZX79C33 is a 33 V, 500 mW Zener diode manufactured by onsemi in DO-35 through-hole axial package. This component is classified as obsolete, indicating discontinued production by the original manufacturer. Equivalent and substitute parts are necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for applications utilizing this voltage regulation component.

Key Parameters

Parameter	Value
Voltage - Zener (Nom)	33 V
Tolerance	±5%
Power - Max	500 mW
Impedance (Max)	80 Ohms
Mounting Type	Through Hole
Package / Case	DO-204AH, DO-35, Axial
Operating Temperature Range	-65°C ~ 200°C

Substitute Part Grouping Explanation

Substitution of the BZX79C33 is determined by the following critical parameters: nominal Zener voltage (33 V), voltage tolerance (±5%), maximum power dissipation capability, package type (through-hole axial), and operating temperature range. Substitute parts are grouped into two categories based on power rating:

Category 1: 500 mW Power Rating (Direct Substitutes) Parts with 500 mW maximum power dissipation in DO-35 package maintain identical power handling and package footprint compatibility with the original BZX79C33.

Category 2: Higher Power Rating (3 W Substitutes) Parts with 3 W maximum power dissipation provide enhanced thermal performance and current handling capacity while maintaining the same 33 V nominal voltage and through-hole axial mounting configuration. These are suitable for applications requiring increased power margin.

Category 3: 400 mW Power Rating (Nexperia Direct Equivalents) Nexperia BZX79-C33 series parts with 400 mW rating represent direct manufacturer equivalents with active product status and RoHS3 compliance.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power Max	Zzt (Max)	Package	Status	RoHS
BZX79C33	onsemi	33 V	±5%	500 mW	80 Ω	DO-35	Obsolete	Not Specified
BZX79-C33,113	Nexperia USA Inc.	33 V	±5%	400 mW	80 Ω	DO-35	Active	RoHS3 Compliant
BZX79-C33,133	Nexperia USA Inc.	33 V	±5%	400 mW	80 Ω	DO-35	Active	RoHS3 Compliant
BZX79-C33,143	NXP Semiconductors	33 V	±5%	400 mW	80 Ω	DO-35	Active	Not Specified
1N3530A	Microchip Technology	33 V	±5%	500 mW	50 Ω	DO-35	Active	RoHS Non-compliant
1N5546B	Microchip Technology	33 V	±5%	500 mW	113 Ω	DO-35	Active	RoHS Non-compliant
1N5748B	Microchip Technology	33 V	±5%	500 mW	90 Ω	DO-35	Active	RoHS Non-compliant
1N5748C	Microchip Technology	33 V	±5%	500 mW	90 Ω	DO-35	Active	RoHS Non-compliant
1N5748D	Microchip Technology	33 V	±5%	500 mW	90 Ω	DO-35	Active	RoHS Non-compliant
1N5937BRLG	onsemi	33 V	±5%	3 W	33 Ω	DO-41	Active	RoHS3 Compliant
1N5078	Microchip Technology	33 V	±5%	3 W	21 Ω	Axial	Active	Not Specified

Engineering Selection Recommendations

Primary Substitutes (Active Status, Recommended)

The Nexperia BZX79-C33 series (part numbers BZX79-C33,113, BZX79-C33,133, and BZX79-C33,143) are direct equivalents with active product status and RoHS3 compliance. These parts maintain identical electrical specifications (33 V nominal, ±5% tolerance, 80 Ω impedance) and package compatibility with the obsolete BZX79C33. The 400 mW power rating is within acceptable margin for applications designed for 500 mW components. High inventory availability (5,787 to 380,891 units) ensures supply continuity.

Secondary Substitutes (Active Status, 500 mW Rating)

Microchip Technology 1N5748 series (1N5748B, 1N5748C, 1N5748D) and 1N5546B provide 500 mW power rating matching the original BZX79C33 specification. These parts are active and available. The 1N5748C and 1N5748D variants offer tighter tolerance (±1%) compared to the original ±5% specification. Operating temperature range is limited to -65°C ~ 175°C, which is narrower than the original -65°C ~ 200°C range. RoHS non-compliance status requires evaluation against design requirements.

Alternative Substitutes (Higher Power Rating)

The 1N5937BRLG (onsemi, 3 W) and 1N5078 (Microchip Technology, 3 W) provide enhanced power dissipation capability in through-hole axial packages. These are suitable for applications requiring increased thermal margin. The 1N5937BRLG is RoHS3 compliant with active status. Operating temperature range for 1N5078 is -65°C ~ 175°C.

Compliance Considerations

Applications requiring RoHS3 compliance should prioritize Nexperia BZX79-C33 series or onsemi 1N5937BRLG. Applications with operating temperature requirements above 175°C must use Nexperia parts or evaluate thermal derating for Microchip alternatives.

Frequently Asked Questions (FAQ)

Q: Can the BZX79-C33,113 replace the obsolete BZX79C33 directly?

A: Yes. The BZX79-C33,113 maintains identical nominal voltage (33 V), tolerance (±5%), impedance (80 Ω), and package (DO-35). The 400 mW power rating is within acceptable operating margin for applications designed for 500 mW. This part is active with RoHS3 compliance and high inventory availability.

Q: What is the difference between the Nexperia BZX79-C33,113, BZX79-C33,133, and BZX79-C33,143?

A: All three parts are electrically identical with 33 V nominal voltage, ±5% tolerance, 400 mW power rating, and 80 Ω impedance. Differences exist in packaging format: BZX79-C33,113 and BZX79-C33,133 are supplied in Cut Tape (CT), while BZX79-C33,143 is supplied in Bulk. Selection depends on procurement and assembly requirements.

Q: Can I use a 3 W Zener diode (1N5937BRLG or 1N5078) as a substitute?

A: Yes. Higher power rating components are suitable for applications requiring increased thermal performance and current handling. The 1N5937BRLG maintains the same 33 V nominal voltage and through-hole axial package. The 1N5078 provides similar electrical performance with lower impedance (21 Ω). Both are compatible with the original circuit topology.

Q: What are the operating temperature limitations for substitute parts?

A: The original BZX79C33 operates from -65°C to 200°C. Nexperia BZX79-C33 series maintains this range. Microchip Technology alternatives (1N5546B, 1N5748 series, 1N5078) are limited to -65°C to 175°C. Applications requiring operation above 175°C must use Nexperia parts.

Q: Are there RoHS compliance differences between substitutes?

A: Yes. Nexperia BZX79-C33 series and onsemi 1N5937BRLG are RoHS3 compliant. Microchip Technology parts (1N3530A, 1N5546B, 1N5748 series, 1N5078) are RoHS non-compliant. Design requirements and customer specifications determine which compliance status is necessary.

Q: How do impedance values affect substitution?

A: Impedance (Zzt) affects dynamic response and noise characteristics. The original BZX79C33 specifies 80 Ω maximum impedance. Nexperia equivalents maintain 80 Ω. Microchip 1N3530A offers lower impedance (50 Ω), while 1N5546B is higher (113 Ω). Lower impedance provides better high-frequency performance; higher impedance may affect transient response. Circuit-level evaluation is necessary for impedance-sensitive applications.

Q: What inventory considerations apply to these substitutes?

A: Nexperia BZX79-C33,143 has the highest inventory (380,891 units), followed by BZX79-C33,113 (20,400 units) and BZX79-C33,133 (5,787 units). Microchip alternatives range from 720 to 1,118 units. onsemi 1N5937BRLG has 3,988 units available. Inventory levels support long-term supply continuity for all recommended substitutes.

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