BZX79C24 Equivalent & Substitute Parts

Part Overview

The BZX79C24 is a 24 V, 500 mW Zener diode manufactured by onsemi in DO-35 (DO-204AH) axial through-hole package. This component is classified as obsolete, though 43,300 pieces remain in stock as new original inventory. The BZX79C24 functions as a voltage regulation and transient protection device in electronic circuits requiring 24 V reference voltage with ±5% tolerance.

Due to the obsolete product status, equivalent and substitute Zener diodes with matching or superior electrical characteristics are available from active product lines. Substitutes maintain the 24 V nominal Zener voltage and 500 mW power rating while offering improved availability, compliance certifications, and in some cases enhanced performance specifications.

Key Parameters

Parameter	BZX79C24	Unit
Voltage - Zener (Nom)	24	V
Tolerance	±5%	—
Power - Max	500	mW
Impedance (Max)	70	Ohms
Current - Reverse Leakage @ Vr	50 nA @ 16.8 V	nA
Voltage - Forward (Max) @ If	1.5 V @ 100 mA	V
Operating Temperature Range	-65°C to 200°C	°C
Mounting Type	Through Hole	—
Package / Case	DO-204AH, DO-35, Axial	—

Substitute Part Grouping Explanation

Substitution of the BZX79C24 is determined by the following critical parameters:

Primary Matching Criteria:

Voltage - Zener (Nom): 24 V (exact match required)
Tolerance: ±5% or tighter (±1% acceptable; ±10% acceptable with design review)
Power - Max: 500 mW or greater
Mounting Type: Through Hole
Package / Case: DO-35 (DO-204AH) or equivalent axial configuration

Secondary Compatibility Factors:

Impedance (Max): 70 Ohms or lower preferred for circuit stability
Current - Reverse Leakage: 50 nA or lower preferred
Voltage - Forward (Max): 1.5 V or lower at specified current
Operating Temperature Range: Minimum -65°C to 175°C or better

Substitute parts are grouped into two categories:

Category A - Direct Electrical Equivalents (500 mW, DO-35 Package): Parts with identical 24 V, 500 mW specifications in DO-35 package. These include 1N3527A, 1N5252A (DO-35), 1N5252B (DO-35), 1N5542B, 1N5745C, 1N5745D, 1N6009A, and 1N6009B. All maintain through-hole axial mounting and support the full operating temperature range of the original part or equivalent.

Category B - Higher Power Alternative (3 W, Axial Package): The 1N5934BRLG offers 3 W power dissipation with 24 V nominal voltage and ±5% tolerance. This part is suitable for applications requiring higher power handling while maintaining the same voltage regulation function.

Category C - Direct Manufacturer Equivalent (400 mW, ALF2 Package): The BZX79-C24,133 from Nexperia USA Inc. is a direct equivalent with 24 V, 400 mW specifications and identical impedance (70 Ohms). The ALF2 package is mechanically compatible with DO-35 applications.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Impedance (Max)	Package	Product Status	RoHS Status
BZX79C24	onsemi	24 V	±5%	500 mW	70 Ω	DO-35	Obsolete	—
BZX79-C24,133	Nexperia USA Inc.	24 V	±5%	400 mW	70 Ω	ALF2	Active	ROHS3 Compliant
1N3527A	Microchip Technology	24 V	±5%	500 mW	38 Ω	DO-35	Active	RoHS non-compliant
1N5252A (DO-35)	Microsemi Corporation	24 V	±10%	500 mW	33 Ω	DO-35	Active	RoHS non-compliant
1N5252B (DO-35)	Microchip Technology	24 V	±5%	500 mW	33 Ω	DO-35	Active	RoHS non-compliant
1N5542B	Microchip Technology	24 V	±5%	500 mW	109 Ω	DO-35	Active	RoHS non-compliant
1N5745C	Microchip Technology	24 V	±1%	500 mW	70 Ω	DO-35	Active	RoHS non-compliant
1N5745D	Microchip Technology	24 V	±1%	500 mW	70 Ω	DO-35	Active	RoHS non-compliant
1N6009A	Microchip Technology	24 V	±10%	500 mW	78 Ω	DO-35	Active	RoHS non-compliant
1N6009B	Microchip Technology	24 V	±5%	500 mW	62 Ω	DO-35	Active	RoHS non-compliant
1N5934BRLG	onsemi	24 V	±5%	3 W	19 Ω	DO-41	Active	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Identical Electrical Performance):

The 1N5252B (DO-35) and 1N5745D are the primary direct replacements for the BZX79C24. Both maintain 24 V nominal voltage, 500 mW power rating, and DO-35 package configuration. The 1N5252B offers lower impedance (33 Ω) compared to the original 70 Ω specification, providing improved voltage regulation stability. The 1N5745D maintains the original 70 Ω impedance with tighter ±1% tolerance, suitable for precision voltage reference applications. Both parts are in active production status with current inventory availability.

For Improved Compliance:

The BZX79-C24,133 from Nexperia USA Inc. is an active product with ROHS3 compliance certification. This part provides direct electrical equivalence with 24 V, ±5% tolerance, and identical 70 Ω impedance. The 400 mW power rating is slightly lower than the original 500 mW specification but remains suitable for most circuit applications. The ALF2 package is mechanically compatible with DO-35 through-hole mounting.

For Higher Power Applications:

The 1N5934BRLG offers 3 W power dissipation with 24 V nominal voltage and ±5% tolerance. This part is suitable for circuits requiring higher transient energy absorption or continuous power dissipation. The DO-41 axial package is mechanically compatible with DO-35 footprints. This part carries ROHS3 compliance and active product status.

For Precision Voltage Reference:

The 1N5745C and 1N5745D both provide ±1% tolerance, superior to the original ±5% specification. These parts are suitable for applications requiring tighter voltage regulation accuracy. Both maintain 500 mW power rating and DO-35 package configuration.

Compliance Considerations:

The original BZX79C24 carries no RoHS compliance designation. Most substitute parts from Microchip Technology and Microsemi Corporation are RoHS non-compliant, maintaining compatibility with legacy circuit designs. The BZX79-C24,133 (Nexperia) and 1N5934BRLG (onsemi) are ROHS3 compliant, suitable for applications requiring environmental compliance certifications.

Frequently Asked Questions (FAQ)

Q: Can the 1N5252B (DO-35) directly replace the BZX79C24 without circuit modification?

A: Yes. The 1N5252B maintains the same 24 V nominal voltage, ±5% tolerance, 500 mW power rating, and DO-35 package. The lower impedance (33 Ω versus 70 Ω) improves voltage regulation performance without requiring circuit changes. Both parts are through-hole axial components with identical mounting compatibility.

Q: What is the difference between the 1N5745C and 1N5745D?

A: Both parts are electrically identical with 24 V nominal voltage, ±1% tolerance, 500 mW power rating, 70 Ω impedance, and DO-35 package. The designation difference reflects manufacturing lot or date code variations. Both are suitable direct replacements for the BZX79C24.

Q: Is the 1N5934BRLG (3 W) suitable for applications designed for the 500 mW BZX79C24?

A: Yes. The 1N5934BRLG provides higher power dissipation capability (3 W versus 500 mW) with identical 24 V nominal voltage and ±5% tolerance. The higher power rating ensures the part operates within safe thermal limits in applications with higher transient energy or continuous power requirements. The DO-41 axial package is mechanically compatible with DO-35 through-hole footprints.

Q: Why do some substitute parts have ±10% tolerance instead of ±5%?

A: The 1N5252A (DO-35) and 1N6009A offer ±10% tolerance, which is wider than the original ±5% specification. These parts are suitable for applications where voltage regulation tolerance is not critical. For circuits requiring ±5% or tighter tolerance, select parts with matching or superior tolerance specifications such as 1N5252B, 1N5745C, or 1N5745D.

Q: What is the operating temperature range difference between the BZX79C24 and substitute parts?

A: The original BZX79C24 operates from -65°C to 200°C. Most substitute parts operate from -65°C to 175°C, a 25°C reduction in maximum temperature. For applications requiring operation above 175°C, the BZX79C24 or equivalent high-temperature variants must be specified. For standard industrial and commercial applications (-40°C to 85°C ambient), the temperature difference is not a limiting factor.

Q: Is the BZX79-C24,133 (ALF2 package) mechanically compatible with DO-35 circuit board layouts?

A: Yes. The ALF2 package is an axial through-hole configuration mechanically compatible with DO-35 (DO-204AH) footprints. Both packages use identical lead spacing and mounting hole diameter. The BZX79-C24,133 provides ROHS3 compliance with active product status and identical electrical specifications (24 V, ±5%, 70 Ω impedance).

Q: Which substitute part offers the lowest impedance for improved voltage regulation?

A: The 1N5252A (DO-35) and 1N5252B (DO-35) both offer 33 Ω impedance, the lowest among available substitutes. Lower impedance provides better voltage regulation performance and faster transient response. The 1N5252B is preferred due to ±5% tolerance matching the original specification.

Q: Are all substitute parts available in the same packaging format as the BZX79C24?

A: All substitute parts except the 1N5934BRLG are available in DO-35 (DO-204AH) axial through-hole package, identical to the BZX79C24. The 1N5934BRLG uses DO-41 axial package, which is mechanically compatible with DO-35 footprints but offers higher power dissipation (3 W). The BZX79-C24,133 uses ALF2 package, also mechanically compatible with DO-35 layouts.

Q: What is the reverse leakage current specification, and why does it vary among substitute parts?

A: Reverse leakage current is the small current flowing through the Zener diode when reverse-biased below the Zener voltage. The BZX79C24 specifies 50 nA @ 16.8 V. Substitute parts range from 10 nA to 100 nA at different reverse voltages. Lower reverse leakage improves circuit performance in precision applications. The 1N5542B offers the lowest leakage (10 nA @ 21.6 V), while most other parts specify 100 nA at similar reverse voltages.

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