Use when working with transistor similarity calculations - comparing BJT MPNs, understanding NPN/PNP polarity matching, equivalent groups like 2N2222/PN2222, or transistor-specific similarity logic.
Guidance for working with TransistorSimilarityCalculator in the lib-electronic-components library.
For metadata-driven similarity architecture, see /similarity-metadata:
The TransistorSimilarityCalculator compares bipolar junction transistors (BJTs) based on:
ComponentType.TRANSISTOR
ComponentType.TRANSISTOR_NXP
ComponentType.TRANSISTOR_VISHAY
// Any type starting with "TRANSISTOR_"
Note: Does NOT apply to MOSFETs - use MosfetSimilarityCalculator for those.
HIGH_SIMILARITY = 0.9; // Equivalent parts
MEDIUM_SIMILARITY = 0.7; // Same family, compatible
LOW_SIMILARITY = 0.3; // Same category, different specs or polarity
The calculator knows these equivalent groups:
| Group | Members |
|---|---|
| 2N2222 family | 2N2222, 2N2222A, PN2222, PN2222A |
| 2N3904 family | 2N3904, PN3904 |
| 2N3906 family | 2N3906, PN3906 |
| 2N2907 family | 2N2907, 2N2907A, PN2907, PN2907A |
| BC547 family | BC547, BC547A, BC547B, BC547C |
| BC557 family | BC557, BC557A, BC557B, BC557C |
NPN and PNP transistors always return LOW_SIMILARITY (0.3)
| Comparison | Result |
|---|---|
| 2N2222 (NPN) vs PN2222 (NPN) | 0.9 (equivalent) |
| 2N2222 (NPN) vs 2N2907 (PNP) | 0.3 (different polarity) |
| 2N3904 (NPN) vs 2N3906 (PNP) | 0.3 (complementary pair, different polarity) |
The calculator ignores common suffixes:
-T, -TR, -TA (tape/reel packaging)A, B, C (grade suffixes on BC series)calculator.calculateSimilarity("2N2222", "2N2222-T", registry);
// Returns 0.9 (same transistor, different packaging)
calculator.calculateSimilarity("2n2222", "2N2222", registry);
// Returns 0.9 (case insensitive)
// Equivalent parts
calculator.calculateSimilarity("2N2222", "PN2222", registry);
// Returns 0.9
// Same part with variant
calculator.calculateSimilarity("2N2222", "2N2222A", registry);
// Returns 0.9
// NPN vs PNP
calculator.calculateSimilarity("2N2222", "2N2907", registry);
// Returns 0.3
// Different families
calculator.calculateSimilarity("2N2222", "BC547", registry);
// Returns 0.3
// Non-transistor parts
calculator.calculateSimilarity("LM358", "MC1458", registry);
// Returns 0.0
sim(A,B) == sim(B,A)2N prefix: JEDEC standard (2N2222, 2N3904, etc.)PN prefix: Often equivalent to 2N (PN2222 ≈ 2N2222)BC prefix: European standard (BC547, BC557)MPS prefix: Motorola/ON Semi (MPS2222A ≈ 2N2222A)