{"id": "card_n_0fa594da0bff", "kind": "note", "title": "Diode — the exponential gate", "body": "The diode's current grows exponentially with voltage; sealed exactly: e^(x+ln2) = 2e^x —\ncurrent DOUBLES for every ln2·nVT of forward voltage, ≈ 17.9 mV at room temperature (sealed:\nfloor(10⁴·ln2·0.02585) = 179): https://narrowhighway.com/s/1ee0d3ed486453eee0967146a531984888709198b39fb16a7b2c2a5f58ef1b73 . That knife-edge nonlinearity is why a diode can\nrectify — turn a symmetric radio wave into a one-way signal. The honest boundary: the famous\n'0.7 V drop' is a silicon rule of thumb (germanium ~0.3 V, LEDs 2–3 V) — material constants\nare measured, and deriving them needs semiconductor band physics, not a one-line formula.", "source": {"label": "Concordance assay — 2026-07-09", "url": "https://narrowhighway.com/s/1ee0d3ed486453eee0967146a531984888709198b39fb16a7b2c2a5f58ef1b73", "ref": "electronics_dig", "authority_tier": "engine_derived"}, "shelf": "science", "box": "electronics", "bands": ["diode", "shockley", "exponential", "rectifier", "electronics", "semiconductor"], "connections": [], "author": "engine", "created_at": "2026-07-10T00:59:49.508624+00:00", "updated_at": "2026-07-10T00:59:49.508624+00:00", "visibility": "public", "lifecycle_stage": "public", "volatility": "permanent", "surface": "secular", "metrics": {"paperclips_count": 0, "helpful_count": 0, "not_helpful_count": 0, "cite_count": 0, "walks_through_count": 0, "flagged_count": 0}, "source_hash": "8d3549726c00178e17551e9e0c666b6b069fcadaa4bb6bbaf21e544825e3e34b"}