bwsign

confirmedupstream bugPython · python-controlSystems & data structuresJuly 25, 2026

the question

Does python-control's LTISystem.bandwidth return the correct bandwidth for a stable system with negative DC gain?

what came out

python-control LTISystem.bandwidth tests the magnitude drop with the signed DC gain but bisects with abs(dcgain); for any negative-DC-gain system the drop set is empty and it returns infinity where the true bandwidth is finite (0.9976 first-order, 2.0178 second-order). Identical magnitude responses confirm the sign is irrelevant.

method & receipts

Result: confirmed
Reproducible — one script re-runs the whole thing from scratch.
Tested — a correctness/benchmark suite ships alongside the code.

→ read the code and re-run it

github.com/v-code01/bwsign