MOSFET Similarity Calculator Skill

Guidance for working with MosfetSimilarityCalculator in the lib-electronic-components library.

For metadata-driven similarity architecture, see /similarity-metadata:

• SpecImportance levels (CRITICAL, HIGH, MEDIUM, LOW, OPTIONAL)
• ToleranceRule types (exactMatch, percentageTolerance, minimumRequired, etc.)
• SimilarityProfile contexts (DESIGN_PHASE, REPLACEMENT, COST_OPTIMIZATION, etc.)
• Calculator integration patterns and gotchas

Overview

The MosfetSimilarityCalculator compares MOSFETs based on:

• Equivalent groups - Cross-manufacturer equivalents
• Channel type - N-channel vs P-channel
• Electrical characteristics - Voltage, current ratings

Applicable Types

ComponentType.MOSFET
ComponentType.MOSFET_INFINEON
ComponentType.MOSFET_ST
ComponentType.MOSFET_NXP
// Any type starting with "MOSFET_"

Note: Returns true for null type to handle unrecognized MOSFETs.

Similarity Thresholds

HIGH_SIMILARITY = 0.9;   // Equivalent parts
MEDIUM_SIMILARITY = 0.7; // Similar specs
LOW_SIMILARITY = 0.3;    // Different channel type or specs

Equivalent Groups

The calculator knows these cross-manufacturer equivalents:

Channel Type Rules

N-channel and P-channel MOSFETs always return LOW_SIMILARITY (0.3)

calculator.calculateSimilarity("IRF530", "IRF9530", registry);
// Returns 0.3 (N vs P channel)

Manufacturer Prefix Handling

The calculator normalizes manufacturer prefixes:

calculator.calculateSimilarity("IRF530", "STF530", registry);
// Returns 0.9 (same part, different manufacturer)

Suffix Handling

Common suffixes that don't affect equivalence:

• N - Updated version (IRF530N ≈ IRF530)
• PBF - Lead-free
• L - Logic level gate

calculator.calculateSimilarity("IRF530", "IRF530N", registry);
// Returns 0.9 (same MOSFET, N is just version)

Test Examples

// Cross-manufacturer equivalent
calculator.calculateSimilarity("IRF530", "STF530", registry);
// Returns 0.9

// N-channel vs P-channel
calculator.calculateSimilarity("IRF530", "IRF9530", registry);
// Returns 0.3

// Different current ratings
calculator.calculateSimilarity("IRF530", "IRF540", registry);
// Returns < 0.9 (14A vs 28A)

// Non-MOSFET parts
calculator.calculateSimilarity("LM358", "LM324", registry);
// Returns 0.0

Implementation Notes

• Returns 0.0 for non-MOSFET MPNs
• The 9 in part number typically indicates P-channel
• Symmetry: sim(A,B) == sim(B,A)

Learnings & Quirks

Part Number Patterns

• IRF5xx/IRF6xx: N-channel power MOSFETs
• IRF95xx/IRF96xx: P-channel equivalents
• The xx number often indicates Vds rating (e.g., 530 ≈ 100V)

Cross-Manufacturer Equivalence

• STF = ST equivalent to IRF
• Many manufacturers make "drop-in" replacements
• Check Vds, Rds(on), and Id specs for true equivalence

Package Variants

• TO-220: Standard through-hole
• TO-220F: Isolated tab
• D-PAK: Surface mount
• Same electrical part in different package = HIGH_SIMILARITY