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:

| IRF Part | Equivalents | |----------|-------------| | IRF530 | STF530, IRF530N, STF530N | | IRF540 | STF540, IRF540N, STF540N | | IRF9530 | STF9530, IRF9530N (P-channel) | | IRF9540 | STF9540, IRF9540N (P-channel) |

Channel Type Rules

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

| Part | Channel | Note | |------|---------|------| | IRF530 | N-channel | Standard power MOSFET | | IRF9530 | P-channel | The "9" indicates P-channel | | IRF540 | N-channel | Higher current than IRF530 | | IRF9540 | P-channel | Higher current P-channel |

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

Manufacturer Prefix Handling

The calculator normalizes manufacturer prefixes:

| Manufacturer | Prefix | Example | |--------------|--------|---------| | International Rectifier | IRF | IRF530 | | STMicroelectronics | STF | STF530 | | Vishay | IRF, SIF | SIF530 | | Infineon | IPD, IPB | IPD530 |

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