BZX55C33 Equivalent & Substitute Parts

Part Overview

The BZX55C33 is a Zener diode rated at 33 V nominal voltage with 500 mW maximum power dissipation, manufactured by onsemi in a DO-35 through-hole axial package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement continuity. The BZX55C33 serves voltage regulation and protection applications requiring precise 33 V reference characteristics with ±6% tolerance.

Substiute Parts

BZX55C33

onsemiIn Stock: 5428BZX55C33 Datasheet

Current PartRFQ

1N5078

Microchip TechnologyIn Stock: 8311N5078 Datasheet

SimilarRFQ

BZX79C33

Taiwan Semiconductor CorporationIn Stock: 4471BZX79C33 Datasheet

Parametric EquivalentRFQ

BZX79C33-T50A

Fairchild SemiconductorIn Stock: 30719BZX79C33-T50A Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the BZX55C33 is determined by the following critical parameters:

Primary Matching Criteria:

• Zener voltage: 33 V nominal
• Package type: DO-35 through-hole axial configuration
• Mounting: Through-hole compatible with axial lead spacing
• Power rating: 500 mW or higher
• Impedance: 80 Ohms maximum

Secondary Compatibility Factors:

• Tolerance: ±5% or tighter (acceptable improvement over ±6%)
• Reverse leakage current: 50 nA or lower (acceptable improvement)
• Operating temperature range: -65°C minimum and 175°C or higher maximum
• Forward voltage: 1.5 V or lower at 100 mA

The substitute parts listed below meet or exceed the primary matching criteria and maintain functional equivalence within the specified electrical and mechanical constraints.

Parameter Comparison

Engineering Selection Recommendations

BZX79C33 (Taiwan Semiconductor Corporation)

The BZX79C33 is the primary parametric equivalent for the BZX55C33. Both components share identical zener voltage (33 V), power rating (500 mW), impedance (80 Ohms), and DO-35 package configuration. The BZX79C33 offers improved tolerance (±5% versus ±6%) and lower reverse leakage current (50 nA versus 100 nA). The component is active in production status and REACH compliant. Operating temperature range is -65°C to 175°C, which covers the lower end of the BZX55C33 range but does not extend to 200°C. This component is suitable for applications where the upper temperature limit does not exceed 175°C.

BZX79C33-T50A (Fairchild Semiconductor)

The BZX79C33-T50A provides identical electrical specifications to the BZX79C33 with the additional advantage of matching the full operating temperature range of the BZX55C33 (-65°C to 200°C). This component maintains 33 V zener voltage, 500 mW power rating, 80 Ohms impedance, and DO-35 package compatibility. The BZX79C33-T50A is active in production. REACH status is listed as affected, requiring compliance verification for applications subject to REACH regulations.

1N5078 (Microchip Technology)

The 1N5078 is a higher-power alternative rated at 3 W maximum power dissipation, compared to 500 mW for the BZX55C33. This component maintains 33 V zener voltage and through-hole axial package configuration. The 1N5078 features improved impedance characteristics (21 Ohms versus 80 Ohms) and tighter tolerance (±5%). However, reverse leakage current is significantly higher (1 µA versus 100 nA). Operating temperature range is -65°C to 175°C. The 1N5078 is suitable for applications requiring higher power dissipation capability but not requiring the lower leakage characteristics of the BZX55C33.

Frequently Asked Questions (FAQ)

Q: Can the BZX79C33 directly replace the BZX55C33 in all applications?

A: The BZX79C33 is electrically equivalent for applications operating within -65°C to 175°C. The BZX55C33 specifies operation to 200°C. Applications requiring operation above 175°C require the BZX79C33-T50A instead.

Q: What is the significance of the impedance difference between BZX55C33 and 1N5078?

A: Impedance (Zzt) affects the dynamic resistance of the zener diode at operating current. The BZX55C33 and BZX79C33 both specify 80 Ohms impedance, while the 1N5078 specifies 21 Ohms. Lower impedance provides better voltage regulation stability. The 1N5078 is suitable where improved regulation is beneficial, but the higher power rating is the primary design driver.

Q: Are the DO-35 and axial package designations interchangeable?

A: DO-35 and axial refer to the same through-hole package configuration for diodes. Both designations describe a component with two axial leads suitable for through-hole PCB mounting. All listed substitute parts use compatible axial lead spacing.

Q: What does REACH Affected status mean for the BZX79C33-T50A?

A: REACH Affected indicates the component may contain substances of concern under European REACH regulations. Applications subject to REACH compliance requirements must verify the specific substance declarations provided by the manufacturer before design implementation.

Q: Why does the 1N5078 have higher reverse leakage current than the BZX55C33?

A: Reverse leakage current is a characteristic of the semiconductor material and junction design. The 1N5078 is designed for higher power dissipation, which typically results in higher leakage current. Applications sensitive to leakage current should use the BZX79C33 or BZX79C33-T50A instead.

Q: Can the BZX55C33 be replaced with a higher voltage zener diode?

A: No. Zener voltage is a critical parameter for voltage regulation and protection circuits. Substitution requires matching the 33 V nominal specification. Using a different voltage rating will result in incorrect circuit operation.

Q: What is the practical difference between ±5% and ±6% tolerance?

A: At 33 V nominal, ±6% tolerance allows ±1.98 V variation (31.02 V to 34.98 V), while ±5% tolerance allows ±1.65 V variation (31.35 V to 34.65 V). Applications with tight voltage regulation requirements benefit from the ±5% tolerance of the substitute parts.