Op-Amp Similarity Calculator Skill

Guidance for working with OpAmpSimilarityCalculator 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 OpAmpSimilarityCalculator compares operational amplifiers based on:

Equivalent families - Known interchangeable parts
Channel count - Single, dual, quad configurations
Characteristics - Bandwidth, slew rate, input type

Applicable Types

ComponentType.OPAMP
ComponentType.OPAMP_TI
ComponentType.OPAMP_ANALOG_DEVICES
ComponentType.OPAMP_ST
// Any type starting with "OPAMP_"

Similarity Thresholds

HIGH_SIMILARITY = 0.9;   // Equivalent parts
MEDIUM_SIMILARITY = 0.7; // Same family, compatible
LOW_SIMILARITY = 0.3;    // Different family

Equivalent Families

Dual Op-Amps (2 channels)

| Family | Members | |--------|---------| | LM358 family | LM358, LM358A, LM358B, MC1458, RC1458 | | TL072 family | TL072, TL072A, TL072B, TL072C | | NE5532 family | NE5532, NE5532A, SA5532, SE5532 |

Quad Op-Amps (4 channels)

| Family | Members | |--------|---------| | LM324 family | LM324, LM324A, LM324N, MC3403, RC3403 | | TL074 family | TL074, TL074A, TL074B, TL074C |

Single Op-Amps

| Family | Members | |--------|---------| | LM741 family | LM741, UA741, MC741, RC741 |

Channel Count Rules

The calculator considers channel count when comparing:

| Comparison | Result | |------------|--------| | LM358 (dual) vs MC1458 (dual) | 0.9 (equivalent) | | LM358 (dual) vs LM324 (quad) | 0.7 (same family, different count) | | LM358 (dual) vs LM741 (single) | 0.7 (same technology, different count) |

Package Suffix Handling

Common suffixes are normalized:

N, P - DIP packages
D, DR - SOIC packages
PW, PWR - TSSOP packages
A, B - Grade variants

calculator.calculateSimilarity("LM358N", "LM358D", registry);
// Returns 0.9 (same op-amp, different package)

Test Examples

// Equivalent dual op-amps
calculator.calculateSimilarity("LM358", "MC1458", registry);
// Returns 0.9

// Same family, different grades
calculator.calculateSimilarity("LM324", "LM324A", registry);
// Returns 0.9

// Dual vs quad (different channel count)
calculator.calculateSimilarity("TL072", "TL074", registry);
// Returns 0.7

// Non-op-amp parts
calculator.calculateSimilarity("IRF530", "2N2222", registry);
// Returns 0.0

Key Characteristics

The calculator may also consider:

GBW (Gain-Bandwidth Product)
Slew Rate
Input Type (JFET vs BJT)
Rail-to-Rail capability

Metadata-Driven Implementation (January 2026)

Status: ✅ Converted (PR #116)

The OpAmpSimilarityCalculator now uses a metadata-driven approach with spec-based comparison.

Specs Compared

| Spec | Importance | Tolerance Rule | Description | |------|-----------|----------------|-------------| | configuration | CRITICAL | exactMatch | Single, dual, quad channel count | | family | HIGH | exactMatch | LM358, TL072, NE5532, etc. | | package | MEDIUM | exactMatch | DIP, SOIC, TSSOP, etc. |

Implementation Details

@Override
public double calculateSimilarity(String mpn1, String mpn2, PatternRegistry registry) {
    // Try metadata-driven approach first
    Optional<ComponentTypeMetadata> metadataOpt = metadataRegistry.getMetadata(ComponentType.OPAMP);
    if (metadataOpt.isPresent()) {
        return calculateMetadataDrivenSimilarity(mpn1, mpn2, metadataOpt.get());
    }
    // Fallback to legacy family-based approach
    return calculateFamilyBasedSimilarity(mpn1, mpn2);
}

Key Features:

Short-circuit check: Different configurations (single vs dual vs quad) return LOW_SIMILARITY immediately
Family boost: Known equivalent families (LM358 ≈ MC1458) boost similarity to HIGH_SIMILARITY
Weighted scoring: totalScore / maxPossibleScore formula for precise comparison
Backward compatible: Falls back to legacy logic if metadata not available

Spec Extraction Methods

// Extract configuration from MPN
private String extractConfiguration(String mpn) {
    if (matchesDualOpAmp(mpn)) return "dual";
    if (matchesQuadOpAmp(mpn)) return "quad";
    if (matchesSingleOpAmp(mpn)) return "single";
    return "";
}

// Extract family from MPN
private String extractFamily(String mpn) {
    // Returns: LM358, LM324, TL072, TL074, NE5532, etc.
}

// Extract package from MPN
private String extractPackageCode(String mpn) {
    // Returns: N, D, DR, PW, P, etc.
}

Behavior Changes

Before (Legacy): Hardcoded equivalent family checks After (Metadata): Configurable specs with weighted importance

| Comparison | Legacy Result | Metadata Result | Notes | |-----------|--------------|-----------------|-------| | LM358 vs MC1458 | 0.9 | 1.0 | Exact configuration + family match | | LM358N vs LM358D | 0.9 | 0.958 | Same op-amp, different package | | LM358 vs LM324 | 0.7 | LOW_SIMILARITY | Short-circuit on configuration mismatch | | TL072 vs TL074 | 0.7 | LOW_SIMILARITY | Different channel count |

Why more accurate: Metadata approach clearly separates configuration (CRITICAL) from package (MEDIUM), providing more precise scoring.

Learnings & Quirks

Naming Conventions

LM prefix: National Semiconductor (now TI)
MC prefix: Motorola (now ON Semi)
TL prefix: TI JFET-input
NE/SA/SE prefix: Signetics (now TI)
UA/RC prefix: Various second sources

Family Relationships

LM358/LM324: Same die, 358 is dual, 324 is quad
TL072/TL074: JFET-input, 072 is dual, 074 is quad
NE5532/NE5534: 5532 is dual, 5534 is single (lower noise)

Cross-Manufacturer Equivalence

LM358 ≈ MC1458 ≈ RC1458 (all dual, general purpose)
LM324 ≈ MC3403 ≈ RC3403 (all quad, general purpose)