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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-mode: "log",
x-label: [Frequency $f$ ($unit("Hz")$)],
y-label: [$e_n(f)$ ($unit("nano volt per shertz")$)],
x-min: 0.1,
x-max: 100000,
y-min: 0.5,
y-max: 50,
x-grid: "minor",
y-grid: "minor",
{
// General purpose (TL072): e_white = 18 nV/sqrt(Hz), fc = 200 Hz
plot.add(
style: (stroke: (dash: "solid")),
label: [TL07x],
domain: (0.1, 100000),
samples: 1000,
f => 18 * calc.sqrt(1 + 200 / f),
)
// Low noise (OPA211): e_white = 1.1 nV/sqrt(Hz), fc = 10 Hz
plot.add(
style: (stroke: (dash: "dashed")),
label: [OPA211],
domain: (0.1, 100000),
samples: 1000,
f => 1.1 * calc.sqrt(1 + 10 / f),
)
// Precision low noise (LT1028): e_white = 0.85 nV/sqrt(Hz), fc = 3.5 Hz
plot.add(
style: (stroke: (dash: "dotted")),
label: [LT1028],
domain: (0.1, 100000),
samples: 1000,
f => 0.85 * calc.sqrt(1 + 3.5 / f),
)
// Chopper stabilized (LTC2057): e_white = 7 nV/sqrt(Hz), fc = 1 Hz
plot.add(
style: (stroke: (dash: "dash-dotted")),
label: [LTC2057],
domain: (0.1, 100000),
samples: 1000,
f => 7 * calc.sqrt(1 + 1 / f),
)
},
)
}),
caption: [Comparison of operational amplifier voltage noise spectral density curves across frequency],
) <figure-opamp-voltage-noise-mathematical-model>
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