BZX79C20 Equivalent & Substitute Parts

Part Overview

The BZX79C20 is a 20 V, 500 mW Zener diode manufactured by onsemi in DO-35 through-hole package. This component is classified as obsolete, though 1045 pieces remain in stock. The BZX79C20 serves as a voltage regulation and protection element in electronic circuits requiring precise 20 V reference voltage with ±5% tolerance.

Due to the obsolete product status, identifying equivalent and substitute parts is necessary for design continuity, long-term supply chain planning, and new production runs. Active alternatives with identical or superior electrical characteristics are available from multiple manufacturers.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	20	V
Tolerance	±5%	%
Power - Max	500	mW
Impedance (Max)	55	Ohms
Current - Reverse Leakage @ Vr	50 nA @ 14 V	nA
Voltage - Forward (Vf) (Max) @ If	1.5 V @ 100 mA	V
Operating Temperature	-65°C ~ 200°C	°C
Mounting Type	Through Hole	—
Package / Case	DO-204AH, DO-35, Axial	—

Substitute Part Grouping Explanation

Substitution of the BZX79C20 is determined by the following critical parameters:

Primary Matching Criteria:

Voltage - Zener (Nom): 20 V (exact match required)
Tolerance: ±5% (acceptable tolerance band)
Power - Max: 500 mW (minimum power rating)
Mounting Type: Through Hole (mechanical compatibility)
Package / Case: DO-35 or equivalent axial package

Secondary Compatibility Factors:

Impedance (Max): 55 Ohms or lower (lower impedance acceptable)
Current - Reverse Leakage: 50 nA @ 14 V or lower (lower leakage acceptable)
Voltage - Forward (Vf): 1.5 V @ 100 mA or lower (lower forward voltage acceptable)
Operating Temperature: -65°C ~ 200°C or equivalent range

Substitute parts are grouped into two categories:

Category A - Direct Electrical Equivalents (500 mW Power Rating): Parts matching all primary criteria with identical 500 mW power rating and DO-35 package.

Category B - Higher Power Alternatives (≥500 mW Power Rating): Parts with superior power handling (3 W) or alternative package configurations (ALF2, Axial) that maintain electrical compatibility while offering enhanced performance margins.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (mW)	Zzt (Ohms)	Vf (Max)	Package	Status
BZX79C20	onsemi	20	±5%	500	55	1.5 V @ 100 mA	DO-35	Obsolete
1N5250B	Microchip Technology	20	±5%	500	25	1.5 V @ 200 mA	DO-35	Active
1N5250B-TR	Vishay General Semiconductor	20	±5%	500	25	1.1 V @ 200 mA	DO-35	Active
1N3525A	Microchip Technology	20	±5%	500	20	1.1 V @ 200 mA	DO-35	Active
1N5250A (DO-35)	Microsemi Corporation	20	±10%	500	25	1.5 V @ 200 mA	DO-35	Active
1N5250B (DO-35)	Microsemi Corporation	20	±5%	500	25	1.5 V @ 200 mA	DO-35	Active
1N4114 (DO35)	Microsemi Corporation	20	±5%	400	150	1 V @ 200 mA	DO-35	Active
BZX79-C20,133	Nexperia USA Inc.	20	±5%	400	55	900 mV @ 10 mA	ALF2	Active
BZX79-C20,143	NXP USA Inc.	20	±5%	400	55	900 mV @ 10 mA	ALF2	Active
1N5932BRLG	onsemi	20	±5%	3000	14	1.5 V @ 200 mA	DO-41	Active

Engineering Selection Recommendations

Primary Substitutes (Recommended for Direct Replacement):

1N5250B-TR (Vishay General Semiconductor) – Active status, ROHS3 compliant, identical 20 V / 500 mW specifications, superior impedance (25 Ohms vs. 55 Ohms), lower forward voltage (1.1 V vs. 1.5 V), DO-35 package, 29,921 units in stock.
1N3525A (Microchip Technology) – Active status, identical 20 V / 500 mW specifications, superior impedance (20 Ohms vs. 55 Ohms), lower forward voltage (1.1 V vs. 1.5 V), DO-35 package, 804 units in stock.
1N5250B (Microchip Technology) – Active status, identical 20 V / 500 mW specifications, superior impedance (25 Ohms vs. 55 Ohms), DO-35 package, 1,415 units in stock.

Secondary Substitutes (Alternative Configurations):

BZX79-C20,143 (NXP USA Inc.) – Active status, ROHS3 compliant, 20 V nominal voltage, ±5% tolerance, 400 mW power rating (80% of original), ALF2 package, 190,035 units in stock. Suitable for applications with reduced power dissipation requirements.
BZX79-C20,133 (Nexperia USA Inc.) – Active status, ROHS3 compliant, 20 V nominal voltage, ±5% tolerance, 400 mW power rating, ALF2 package, 10,400 units in stock.

Higher Power Alternative:

1N5932BRLG (onsemi) – Active status, ROHS3 compliant, 20 V nominal voltage, ±5% tolerance, 3 W power rating (6× original), DO-41 axial package, 300,400 units in stock. Applicable for designs requiring enhanced thermal margin or higher current handling.

Compliance Considerations:

1N5250B-TR, 1N5932BRLG, BZX79-C20,143, and BZX79-C20,133 carry ROHS3 compliance certification.
All listed substitutes maintain REACH Unaffected and EAR99 ECCN status consistent with the original BZX79C20.
Moisture Sensitivity Level (MSL) 1 (Unlimited) applies to all candidates, indicating no moisture-related handling restrictions.

Frequently Asked Questions (FAQ)

Q: Can 1N5250B-TR directly replace BZX79C20 in existing PCB designs?

A: Yes. Both components share identical 20 V nominal voltage, ±5% tolerance, 500 mW power rating, and DO-35 through-hole package. The 1N5250B-TR exhibits superior electrical characteristics (lower impedance and forward voltage), making it a direct functional replacement without circuit modification.

Q: What is the difference between 500 mW and 400 mW Zener diodes in this voltage class?

A: Power rating determines maximum continuous power dissipation capability. The 500 mW BZX79C20 and 1N5250B variants support higher current handling than 400 mW alternatives (BZX79-C20,143, BZX79-C20,133). Selection depends on circuit current requirements. For applications with lower current demands, 400 mW parts are acceptable substitutes.

Q: Are ALF2 package parts compatible with DO-35 footprints?

A: No. ALF2 and DO-35 are distinct through-hole package configurations with different lead spacing and physical dimensions. BZX79-C20,143 and BZX79-C20,133 (ALF2 package) require PCB footprint redesign and cannot be used as drop-in replacements for DO-35 designs without layout modification.

Q: Why does 1N5250A (DO-35) have ±10% tolerance instead of ±5%?

A: Tolerance specification reflects manufacturing process capability and quality grade. The ±10% tolerance of 1N5250A is wider than the ±5% specification of BZX79C20. For applications requiring tighter voltage regulation (±5%), use parts explicitly rated at ±5% tolerance.

Q: Is the 1N5932BRLG (3 W) suitable for all BZX79C20 applications?

A: The 1N5932BRLG is electrically compatible (20 V, ±5%, DO-41 axial package) but physically incompatible with DO-35 footprints. Its 3 W power rating provides thermal margin for high-current applications. Use only if PCB layout accommodates DO-41 package and circuit current exceeds 500 mW dissipation requirements.

Q: What is the significance of impedance (Zzt) differences among substitutes?

A: Impedance affects voltage regulation quality under load changes. Lower impedance (1N3525A at 20 Ohms, 1N5250B at 25 Ohms) provides superior voltage stability compared to the original BZX79C20 (55 Ohms). This represents an improvement for precision voltage reference applications.

Q: Are all listed substitutes in active production status?

A: Yes. All recommended substitutes carry Active product status, ensuring long-term availability and supply chain continuity. The original BZX79C20 is classified as Obsolete, making active alternatives necessary for new designs and production continuity.

Q: Do substitute parts require circuit redesign?

A: Direct electrical substitutes (1N5250B-TR, 1N3525A, 1N5250B) require no circuit modification. Alternative package configurations (ALF2, DO-41) require PCB footprint redesign. Verify package compatibility with existing PCB layout before component selection.

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