BZX84C18-AQ Equivalent & Substitute Parts

Part Overview

The BZX84C18-AQ is an 18 V Zener diode manufactured by Diotec Semiconductor, designed for voltage regulation and protection applications in surface mount configurations. This component operates at a nominal Zener voltage of 18 V with a maximum power dissipation of 300 mW and is housed in a SOT-23-3 (TO-236) package. The part maintains Active product status with 1090 units currently in stock.

Substitute parts are identified when equivalent electrical performance can be achieved within the specified parameter tolerances while maintaining mechanical compatibility. Alternative sources and tolerance grades may be required due to inventory availability, lead time constraints, or application-specific tolerance requirements.

Substiute Parts

BZX84C18-AQ

Diotec SemiconductorIn Stock: 1181BZX84C18-AQ Datasheet

Current PartRFQ

BZX84B18

Diotec SemiconductorIn Stock: 12102BZX84B18 Datasheet

Parametric EquivalentRFQ

BZX84C18

Taiwan Semiconductor CorporationIn Stock: 35251BZX84C18 Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the BZX84C18-AQ is determined by the following critical parameters:

Primary Substitution Criteria:

• Zener voltage nominal value: 18 V (exact match required)
• Maximum power dissipation: 300 mW (equal or greater)
• Package compatibility: SOT-23-3 / TO-236-3 / SC-59 (mechanical interchangeability)
• Mounting type: Surface Mount (identical)
• Impedance maximum: 45 Ohms (equal or lower)

Secondary Compatibility Factors:

• Tolerance grade: ±5% or tighter (±2% acceptable; ±6.39% acceptable with application verification)
• Reverse leakage current: 50 nA or lower at specified voltage
• Operating temperature range: Must encompass or exceed -50°C to 150°C

The identified substitute parts BZX84B18 (Diotec Semiconductor) and BZX84C18 (Taiwan Semiconductor Corporation) meet all primary substitution criteria. Both maintain the 18 V nominal Zener voltage, 300 mW power rating, and SOT-23-3 package specification. Tolerance variations and reverse leakage differences are within acceptable engineering margins for standard voltage regulation applications.

Parameter Comparison

Engineering Selection Recommendations

BZX84B18 (Diotec Semiconductor): This substitute offers tighter tolerance specification (±2%) compared to the main part (±5%), resulting in improved voltage regulation accuracy. Both components share identical manufacturer origin, power rating, impedance characteristics, and operating temperature range. The BZX84B18 is suitable for applications requiring enhanced voltage stability. Significantly higher inventory availability (12070 units) supports extended lead time requirements.

BZX84C18 (Taiwan Semiconductor Corporation): This substitute maintains electrical equivalence across all primary parameters while offering an extended lower operating temperature limit (-65°C versus -50°C). The tolerance specification (±6.39%) is marginally wider than the main part. Reverse leakage current is doubled (100 nA versus 50 nA), which remains acceptable for standard voltage regulation circuits. This option provides the highest inventory availability (35200 units) and ROHS3 compliance certification. The extended temperature range accommodates applications requiring operation in colder environments.

Both substitutes maintain Active product status and are mechanically compatible with existing PCB layouts designed for SOT-23-3 packages. Selection between alternatives depends on tolerance requirements, temperature operating range, and inventory lead time considerations.

Frequently Asked Questions (FAQ)

Q: Can BZX84B18 be used as a direct replacement for BZX84C18-AQ?

A: Yes. Both components share identical nominal Zener voltage (18 V), maximum power dissipation (300 mW), impedance (45 Ohms), and SOT-23-3 package specification. The BZX84B18 features tighter tolerance (±2% versus ±5%), which improves voltage regulation accuracy. Both are manufactured by Diotec Semiconductor and operate across the same temperature range (-50°C to 150°C).

Q: What are the differences between the two substitute options?

A: The BZX84B18 (Diotec) offers ±2% tolerance and 50 nA reverse leakage. The BZX84C18 (Taiwan Semiconductor) provides ±6.39% tolerance, 100 nA reverse leakage, and extended lower temperature operation (-65°C). Both maintain 18 V nominal voltage and 300 mW power rating. Selection depends on tolerance precision requirements and operating temperature specifications.

Q: Are the packages mechanically identical?

A: Yes. All three components use SOT-23-3 (also designated TO-236-3 or SC-59) surface mount packages. PCB footprints, lead spacing, and mounting procedures are identical. No layout modifications are required when substituting between these parts.

Q: Does tolerance grade affect circuit performance?

A: Tolerance grade determines the voltage regulation accuracy. The BZX84B18 (±2%) provides tighter voltage control compared to BZX84C18-AQ (±5%) and BZX84C18 (±6.39%). Applications requiring precise voltage reference should prioritize tighter tolerance specifications. Standard voltage regulation circuits typically accommodate the wider tolerance ranges.

Q: What is the significance of reverse leakage current differences?

A: Reverse leakage current affects circuit quiescent current and temperature stability. The BZX84C18-AQ and BZX84B18 both specify 50 nA leakage, while the Taiwan Semiconductor BZX84C18 specifies 100 nA. For most applications, this difference is negligible. High-impedance circuits or precision analog applications may require the lower leakage option.

Q: Which substitute offers the best inventory availability?

A: The Taiwan Semiconductor BZX84C18 provides the highest stock level (35200 units), followed by BZX84B18 (12070 units). The original BZX84C18-AQ maintains 1090 units in inventory. Availability should be considered when lead time is a critical factor.

Q: Is ROHS compliance a differentiator?

A: The Taiwan Semiconductor BZX84C18 carries ROHS3 compliance certification. The original BZX84C18-AQ and BZX84B18 list RoHS status as "Not applicable." For applications subject to ROHS regulatory requirements, the Taiwan Semiconductor option provides documented compliance.