BZX79-B20,133 Equivalent & Substitute Parts

Part Overview

The BZX79-B20,133 is a 20 V, 400 mW Zener diode manufactured by Nexperia USA Inc. in the DO-204AH (DO-35) axial through-hole package. This component is classified as Active and is ROHS3 compliant. The part is used in voltage regulation and protection circuits where precise 20 V reference voltage is required. Substitute parts are identified when equivalent electrical performance and mechanical compatibility are maintained within the specified parameter tolerances.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	20	V
Tolerance	±2%	-
Power - Max	400	mW
Impedance (Max)	55	Ohms
Current - Reverse Leakage @ Vr	50 nA @ 14 V	-
Voltage - Forward (Max) @ If	900 mV @ 10 mA	-
Operating Temperature Range	-65°C to 200°C	-
Mounting Type	Through Hole	-
Package / Case	DO-204AH, DO-35, Axial	-

Substitute Part Grouping Explanation

Substitution of Zener diodes is determined by the following critical parameters:

Voltage - Zener (Nom): Must be 20 V to maintain circuit reference voltage
Mounting Type: Must be Through Hole to ensure mechanical compatibility
Package / Case: Axial configuration required for board layout compatibility
Power - Max: Must meet or exceed 400 mW to handle circuit power dissipation
Operating Temperature Range: Must support the application's thermal environment
RoHS Status: Must be ROHS3 compliant for regulatory compliance

Substitute parts are grouped into two categories:

Parametric Equivalent: Parts with identical or superior electrical specifications and matching package configuration.

Similar Parts: Parts with the same nominal voltage and through-hole mounting but with variations in power rating, impedance, or package type that may require circuit evaluation.

Parameter Comparison

Parameter	BZX79-B20,133	BZX79-B20,143	1N5250B-TAP	BZT03C20-TR	BZX85B20-TAP
Manufacturer	Nexperia USA Inc.	NXP Semiconductors	Vishay General Semiconductor	Vishay General Semiconductor	Vishay General Semiconductor
Voltage - Zener (Nom)	20 V	20 V	20 V	20 V	20 V
Tolerance	±2%	±2%	±5%	±6%	±2%
Power - Max	400 mW	400 mW	500 mW	1.3 W	1.3 W
Impedance (Max)	55 Ohms	55 Ohms	25 Ohms	15 Ohms	24 Ohms
Current - Reverse Leakage @ Vr	50 nA @ 14 V	50 nA @ 14 V	100 nA @ 15 V	1 µA @ 15 V	500 nA @ 15 V
Voltage - Forward (Max) @ If	900 mV @ 10 mA	900 mV @ 10 mA	1.1 V @ 200 mA	1.2 V @ 500 mA	Not specified
Operating Temperature Range	-65°C to 200°C	-65°C to 200°C	175°C (Max)	175°C (TJ)	-55°C to 175°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	DO-204AH, DO-35, Axial	DO-204AH, DO-35, Axial	DO-204AH, DO-35, Axial	SOD-57, Axial	DO-204AL, DO-41, Axial
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
AEC-Q101 Qualification	Not specified	Not specified	Yes	Not specified	Yes

Engineering Selection Recommendations

BZX79-B20,143 (Parametric Equivalent)

This part is a direct parametric equivalent manufactured by NXP Semiconductors. It maintains identical electrical specifications: 20 V nominal voltage, ±2% tolerance, 400 mW power rating, 55 Ohms maximum impedance, and 50 nA reverse leakage current. The package configuration (DO-204AH, DO-35, Axial) is identical. Both parts are ROHS3 compliant and Active status. This substitute provides equivalent performance with no circuit modifications required.

1N5250B-TAP (Similar Part - Higher Power Rating)

This Vishay part maintains the 20 V nominal voltage and through-hole axial configuration. It provides higher power dissipation capability (500 mW versus 400 mW) and lower impedance (25 Ohms versus 55 Ohms). The tolerance is ±5% compared to ±2% for the original part. This part is AEC-Q101 qualified and ROHS3 compliant. The higher power rating and lower impedance make this suitable for applications requiring enhanced thermal performance, though the relaxed tolerance specification should be evaluated against circuit requirements.

BZX85B20-TAP (Similar Part - Higher Power Rating)

This Vishay part provides the highest power dissipation capability (1.3 W) and maintains ±2% tolerance matching the original part. The impedance is 24 Ohms. The package is DO-204AL (DO-41), which differs from the original DO-35 package and requires board layout verification. Operating temperature range is -55°C to 175°C, which is narrower than the original -65°C to 200°C range. This part is AEC-Q101 qualified and ROHS3 compliant. Selection requires confirmation of board space compatibility due to package differences.

BZT03C20-TR (Similar Part - Highest Power Rating)

This Vishay part offers the highest power dissipation (1.3 W) and lowest impedance (15 Ohms). The package is SOD-57, which differs significantly from the original DO-35 package and requires board layout verification. The tolerance is ±6%, which is wider than the original ±2%. Reverse leakage current is 1 µA at 15 V, which is higher than the original 50 nA at 14 V. This part is ROHS3 compliant. Selection requires confirmation of board space compatibility and evaluation of the relaxed tolerance and higher leakage specifications against circuit requirements.

Frequently Asked Questions (FAQ)

Q: Can BZX79-B20,143 be used as a direct replacement for BZX79-B20,133?

A: Yes. BZX79-B20,143 is a parametric equivalent with identical electrical specifications and package configuration. No circuit modifications are required.

Q: What is the primary difference between the substitute parts?

A: The main differences are power dissipation capability, impedance, tolerance, and package type. BZX79-B20,143 matches the original exactly. 1N5250B-TAP and BZX85B20-TAP offer higher power ratings. BZT03C20-TR offers the highest power rating but uses a different package (SOD-57).

Q: Can I use 1N5250B-TAP in place of BZX79-B20,133?

A: 1N5250B-TAP maintains the 20 V nominal voltage and through-hole axial configuration. It provides higher power dissipation (500 mW versus 400 mW) and lower impedance (25 Ohms versus 55 Ohms). The tolerance is ±5% versus ±2%. This part is suitable if the circuit can tolerate the relaxed tolerance specification.

Q: Why does BZX85B20-TAP have a different package designation?

A: BZX85B20-TAP uses the DO-204AL (DO-41) package, which is physically larger than the DO-35 package of the original part. Both are axial through-hole configurations, but board layout verification is required before substitution.

Q: Is BZT03C20-TR compatible with the original circuit?

A: BZT03C20-TR maintains the 20 V nominal voltage and through-hole mounting. However, it uses the SOD-57 package, which differs from the original DO-35 package. Board layout verification is required. Additionally, the ±6% tolerance and higher reverse leakage current (1 µA versus 50 nA) should be evaluated against circuit specifications.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed are ROHS3 compliant, matching the compliance status of the original BZX79-B20,133.

Q: Which substitute part has the tightest tolerance specification?

A: BZX79-B20,143 and BZX85B20-TAP both maintain ±2% tolerance, matching the original part. 1N5250B-TAP has ±5% tolerance, and BZT03C20-TR has ±6% tolerance.

Q: What is the operating temperature range limitation for substitute parts?

A: The original BZX79-B20,133 operates from -65°C to 200°C. BZX85B20-TAP operates from -55°C to 175°C, which is narrower. 1N5250B-TAP and BZT03C20-TR specify 175°C maximum. Verify that the substitute part's temperature range meets application requirements.

Q: Do any substitute parts have automotive qualification?

A: Yes. 1N5250B-TAP and BZX85B20-TAP are both AEC-Q101 qualified, indicating automotive-grade reliability. The original BZX79-B20,133 and BZX79-B20,143 do not specify AEC-Q101 qualification.

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