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diff --git a/charts/ratio-stability-principle.typ b/charts/ratio-stability-principle.typ
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+// SAME Analog Modular Ecosystem
+//
+// / SPDX-FileCopyrightText: 2026 Denis Chevalier <perso@denischevalier.fr>
+// / SPDX-License-Identifier: CC-BY-SA-4.0
+// / SPDX-License-Identifier: CERN-OHL-S-2.0+
+// / SPDX-License-Identifier: GPL-3.0-or-later
+//
+// The prose, explanatory text, rendered figures, tables, and mathematical
+// content of this specification are licensed under CC BY-SA 4.0. If a later
+// version of CC BY-SA is published, the author grants permission to distribute
+// this work under that later version as well.
+//
+// Hardware designs contained herein (schematics, PCB layouts, mechanical
+// drawings, and CAD models) are licensed under CERN-OHL-S-2.0+.
+//
+// All executable code, helper libraries (`lib/*`), metrology assertions, and
+// embedded verification scripts throughout the source documents are licensed
+// under the GNU General Public License v3.0 or later (GPL-3.0-or-later).
+
+#import "../lib/unify.typ": qty, unit
+#import "@preview/cetz:0.5.2"
+#import "@preview/cetz-plot:0.1.4": plot
+
+#figure(
+  cetz.canvas({
+    import cetz.draw: *
+
+    plot.plot(
+      size: (12, 6),
+      x-label: [Temperature variation $Delta T$ ($unit("celsius")$)],
+      y-label: [Ratio / gain drift $Delta G / G_0$ ($unit("ppm")$)],
+      x-min: 0,
+      x-max: 10,
+      y-min: 0,
+      y-max: 100,
+      x-grid: "minor",
+      y-grid: "minor",
+      {
+        // 10 ppm Metrologic Error Budget Limit
+        plot.add(
+          ((0, 10), (10, 10)),
+          style: (
+            stroke: (paint: luma(120), thickness: 0.8pt, dash: "dash-dotted"),
+          ),
+          label: [Metrologic budget limit],
+        )
+
+        // Unmatched Discrete Resistors (Delta alpha = 50 ppm/°C)
+        plot.add(
+          domain: (0, 10),
+          samples: 1000,
+          style: (stroke: (paint: black, thickness: 1.5pt, dash: "solid")),
+          label: [Unmatched discrete],
+          t => 50 * t,
+        )
+
+        // Matched Discrete Pair (Delta alpha = 1 ppm/°C)
+        plot.add(
+          domain: (0, 10),
+          samples: 1000,
+          style: (stroke: (paint: black, thickness: 1.5pt, dash: "dashed")),
+          label: [Matched discrete pair],
+          t => 1 * t,
+        )
+
+        // Monolithic Thin-Film Network (Delta alpha = 0.1 ppm/°C)
+        plot.add(
+          domain: (0, 10),
+          samples: 1000,
+          style: (stroke: (paint: black, thickness: 1.5pt, dash: "dotted")),
+          label: [Monolithic thin-film],
+          t => 0.1 * t,
+        )
+      },
+    )
+  }),
+  caption: [Gain drift $Delta G / G_0$ as a function of ambient temperature variation $Delta T$, comparing unmatched discrete resistors, matched discrete pairs, and monolithic thin-film networks against the $qty(10, "ppm")$ Metrologic systematic error budget],
+) <figure-resistor-ratio-tracking-drift>