# A compact model has an unfamiliar inductor topology

A reduced circuit can use a different basis from the drawing. Inspect connectivity, coupling thresholds and the validation report before redrawing the model.

## Compatibility

Manual v1.1.05; historical support semantics

Published guidance with release-applicability limits. Confirm package applicability before following this guide.

## Interpret the reduced model

Historical support explains that compact models can place inductors according to a fundamental-cycle basis. Their placement need not resemble individual segments of the original layout. A changed drawing or ordering can also lead to a different-looking representation.

Treat an unfamiliar representation as a modelling question to verify, rather than relocating elements solely to make the schematic look symmetric.

## Check coupling and completeness

1. Check that the intended ports, junctions and connections are present.
2. Inspect THRESHOLD_K and the matching manual. Removing small couplings changes retained numerical information; a large threshold can remove important coupling.
3. Compare the reduced circuit's response in an appropriate testbench, as well as the extraction diagnostics.
4. If a junction or scaling term is missing, record the exact version and a minimal example. Historical fixes do not establish that a new report has the same cause.

## Limit of a small residual

A low fitting residual alone does not validate the chosen circuit topology or prove the reduced model behaves correctly in its intended application.

## Sources and verification details

Recorded inputs/builds only. Complete walkthrough and final-package acceptance remain separate.



- published:lvs-manual-1.1.05: Compact-model settings, including THRESHOLD_K
- support:SUP-020: Historical fundamental-cycle and omitted-coupling explanations
- owner:technical-review-20261102: Owner accepted this modelling explanation; version limits and execution scope retained

- The owner accepted the modelling explanation on 2 November 2026. Applicable release/platform and unrecorded walkthrough checks remain pending.

## Related guides

- [An extracted resistance or inductance looks unphysical](/knowledge-base/inductex-negative-resistance)
- [Why are series components reported together with ++ or --?](/knowledge-base/inductex-merged-series-values)
- [Start an LVS comparison with the correct settings and technology files](/knowledge-base/lvs-first-settings)