BenchBridge

A browser-based digital twin of the Analog Devices ADALM2000 (M2K) USB instrument, styled after the Scopy software interface. Draw a circuit, measure it with a full bench of virtual instruments, and transfer it to a solderless breadboard — all in the browser, no hardware and nothing to install.

▶ Live app: https://bridgem2k.onrender.com

The twin teaches the ideal and parametric side of measurement so students arrive at the real bench already fluent in the instruments. It is course-agnostic — built for introductory analog and mixed-signal courses generally, not tied to any single class.

Scope: this is an analog digital twin. It models the M2K's analog instruments — oscilloscope, signal generator, spectrum analyzer, network analyzer, curve tracer, voltmeter, and power supply. The M2K's digital subsystems — the 16-channel logic analyzer, the pattern generator, and the digital I/O / bus (SPI/I²C/UART) tools — are intentionally out of scope and not implemented. Introductory analog and mixed-signal courses use only the analog bench, so the twin mirrors exactly that.

Differential measurement (like the real hardware)

The M2K's scope inputs are differential, and so are the twin's. Each oscilloscope channel measures the voltage between its + and − probes (CH1 = 1+ minus 1−, CH2 = 2+ minus 2−), not just a node referenced to ground. This is a first-class capability throughout the app, and it is what makes the parametric measurements possible:

• Probe a floating component — read the voltage across a part that isn't tied to ground.
• Reject common-mode — measure a small difference riding on a large shared offset.
• Sense current as a voltage — read differentially across a sense resistor, the basis of the diode/transistor I-V curves (XY mode) and the Curve Tracer.

Wire the 1−/2− probes in the schematic to set the negative input; leave them unwired for an ordinary single-ended (node-to-ground) reading.

Instruments

• Signal Generator — two channels (W1/W2): sine, square (variable duty cycle), triangle, sawtooth; configurable frequency, amplitude, DC offset.
• Oscilloscope — two true differential channels (1+/1−, 2+/2−) with per-channel Volts/div and offset, edge and pulse/width triggers, holdoff, auto/normal/single modes, a measurements row (Vpp, Vrms, mean, frequency, duty), cursors, and an XY mode (CH1 vs CH2) for I-V curves and Lissajous figures.
• Spectrum Analyzer — single-sided amplitude spectrum in dBFS via a Bluestein N-point FFT (no zero-padding leakage), with five windows (Hanning, Hamming, Blackman, Flat-top, Rectangle), running average and persistence, a parabolic-interpolated peak marker, a theoretical harmonic overlay, and a Learning Mode ADC bit-depth selector (4/8/12-bit) (noise floor shifts ~6 dB/bit; SNR from the Walden formula).
• Network Analyzer — Bode magnitude + phase by sine-sweeping the drawn circuit through ngspice .ac, with a −3 dB cursor and live value tuning.
• Curve Tracer — parametric device characteristic curves, traced the hardware-faithful way: W1 sweeps the main terminal while W2 steps the controlling parameter, read differentially across a sense resistor in scope XY. Produces a family of BJT collector curves (Ic-Vce stepped by base current) or MOSFET drain curves (Id-Vds stepped by Vgs). Single diode/Zener I-V curves come straight from the scope's XY mode.
• Voltmeter and Power Supply — DC node measurements and ±5 V rails for powering active circuits.
• Export PNG — every instrument (and the schematic and breadboard) has an Export PNG button in its header, saved through the browser's native Save dialog (name + folder). Instrument plots export on their dark screen background; the schematic and breadboard export as clean white paper figures — ready to drop into a prelab or report.

Circuit editor + simulation

• Schematic editor — place and wire R, C, L, diodes (plain / LED with settable Vf / Zener with settable breakdown), transistors (BJT 2N3904 / 2N3906, MOSFET ZVN / ZVP), a selectable op-amp (the ADALP2000 kit's OP27, OP37, OP97, OP482, OP484, plus the course TLV9062 — a single-supply rail-to-rail dual used in the photodiode transimpedance example — each a behavioural model of the real part, with bandwidth/slew/output-swing matched to its datasheet, a "not in your parts kit" badge for off-kit choices, and per-part gotcha warnings such as OP37's decompensation below gain 5), the INA125 instrumentation amp, generator/scope/supply ports, and ground. Every active part is a real, packaged device — there is no package-less "ideal" op-amp or in-amp. Passive R/C/L accept any value but also offer a quick-pick palette of the ADALP2000 kit's stocked values (plus the kit's potentiometers, thermistor, and a polarized electrolytic), with an optional "nearest kit value" snap so students design with what they physically have. Connections are marked with junction dots, and dragging a part rubber-bands its wires — a "touch" connection (two pins on one node) turns into a real wire when the part moves, so nothing silently disconnects. Includes a Selected-panel part-kind picker, undo/redo (Ctrl+Z / Ctrl+Y), copy/paste/cut (Ctrl+C/V/X), box-select and group move, rotate, and Save/Open to .json.
• SPICE simulation — ngspice compiled to WebAssembly runs in a Web Worker, so the generator → circuit → scope/Bode loop is fully in-browser. The generator drives the circuit input; the scope and spectrum read the circuit output node (single-ended, or differentially across two probes).
• Breadboard — transfer a drawn schematic to a parametric solderless board (2-pin parts, transistors in a TO-92 footprint, op-amps as their real DIP package (8-pin single for OP27/37/97, 14-pin quad for OP482/484, the TLV9062 on a SOIC-8-to-DIP adapter), and the INA125 as a 16-pin DIP), run jumpers, and Check that the board is electrically equivalent to the schematic, with per-connection feedback (including the INA125's required reference/sense/sleep straps). The board provides fixed M2K connector strips with pre-wired, colour-coded power rails (V+ red, V− blue, GND neutral), and jumpers on a supply net take that rail's colour. Resistor legs enforce a realistic minimum hole spacing. Practice mode colours nets live; Bench mode hides them until Check. The combined view has a draggable splitter and a stacked / side-by-side toggle. Save/Open a "lab" bundle (schematic + board + generator settings) as one file.

Example library

An Examples menu in the Circuit editor loads ready-made circuits, each pre-wired with a source and probes and (where useful) a preset generator drive and scope mode:

• Getting started: a Flashlight (supply → resistor → LED) and a bare signal (W1 → scope) to learn the bench before any theory.
• Passive: voltage divider, RC low/high-pass, LC low/high-pass, RL low/high-pass, RLC band-pass, and a Diode I-V curve (loads straight into XY mode with a triangle sweep, read differentially across the sense resistor).
• Amplifiers: inverting, non-inverting, integrator, differentiator, and a two-input summing amp (all the kit OP484), plus an INA125 instrumentation-amp example (gain 10 set by an external R_G).
• Transimpedance (current → voltage): a single-supply photodiode TIA on the TLV9062 (light drives the output up from a small reference; open the Network Analyzer's Transimpedance mode to see |Z| flat at R_f then roll off), and an AC transimpedance amp on the OP484.

Layouts

A Layouts dropdown arranges multiple instruments at once (Generator + Spectrum, Generator + Scope, Circuit + Network/Bode, Circuit + Scope, Scope + Supply + Voltmeter), or view any single instrument full-window.

Running locally

npm install
npm run dev

Open the URL Vite prints (e.g. http://localhost:5173/benchbridge/). Run npm test for the core-math test suite.

Building

npm run build

Output goes to dist/. The app is fully static (no backend).

Deploying

The build is fully static (dist/), no backend. The live site runs on Render via the included render.yaml Blueprint (served at root, BASE_PATH=/); it also deploys to GitHub Pages at the /benchbridge/ subpath, the default base (npx gh-pages -d dist). The base path is process.env.BASE_PATH || '/benchbridge/'; render.yaml holds the Render specifics.

Tech stack

• React 19 + TypeScript + Vite 8 (no state-management library; state lives in App.tsx and component-local hooks)
• Plotly.js (plotly.js-dist-min) for all plots
• eecircuit-engine (ngspice WASM) for circuit simulation, in a Web Worker
• No backend, no build-time data fetching, no external API calls

Signal math notes

The spectrum uses a Bluestein chirp-Z FFT rather than a zero-padded power-of-2 FFT. For a 1 kHz signal at 100 kSa/s / 16 ms (N = 1600), zero-padding to 2048 points places harmonics at non-integer bins, producing Hanning sidelobes at −30 to −50 dBFS that swamp the noise floor for 8-bit and 12-bit ADC depths. The N-point Bluestein FFT eliminates this entirely.

Quantization noise is synthetic (Gaussian, calibrated to TPDF variance) rather than computed by actual sample quantization, giving the correct statistical appearance of a real ADC noise floor without the deterministic harmonic distortion products that actual quantization introduces.

See CLAUDE.md for the signal-math constitution and docs/ for the engineering conventions, roadmap, and per-phase specs.

License

Copyright © 2026 The Regents of the University of California. Licensed under the MIT License — see LICENSE for the full text. Developed by André Knoesen (UC Davis).