---
name: mosfet-visualizer
description: Use when the user wants to visualize MOSFET IV curves, plot drain current vs drain-to-source voltage, characterize MOSFETs, overlay IV data from multiple devices, compare MOSFET devices, or analyze MOSFET parameters (Vth, Rds_on, gm). Trigger phrases include "MOSFET IV", "IV curves", "characterize MOSFET", "drain current", "Vds vs Id", "plot MOSFET", "MOSFET visualizer", "saturation boundary", "knee point", "curve tracer data".
---

# MOSFET IV Characterization Visualizer

Interactive web-based visualizer for MOSFET IV curves (Id vs Vds). Supports multiple Vgs sweeps, device overlay, saturation boundary detection, and real-time API control.

**Server:** `http://127.0.0.1:8778`
**Source:** `/home/adom/project/mosfet-visualizer/`

## Quick Start

### 1. Ensure the server is running

```bash
curl -sf --max-time 2 http://127.0.0.1:8778/health > /dev/null 2>&1 || bash /home/adom/project/mosfet-visualizer/start-mosfet-visualizer.sh
```

### 2. Open the visualizer

Open a Web View tab pointing to `/proxy/8778/viz` using the workspace API:

```bash
adom-cli hydrogen workspace add-tab \
  --panel-id "<PANE_ID>" \
  --panel-type "adom/a1b2c3d4-0031-4000-a000-000000000031" \
  --display-name "MOSFET IV Visualizer" \
  --display-icon "mdi:chart-line" \
  --initial-state '{"url":"<PROXY_BASE>/proxy/8778/viz"}'
```

Replace `<PANE_ID>` with a leaf pane ID from `adom-cli hydrogen workspace get` and `<PROXY_BASE>` from `$VSCODE_PROXY_URI`.

### 3. Load data

**Sample data:**
```bash
curl -s -X POST http://127.0.0.1:8778/ \
  -H 'Content-Type: application/json' \
  -d '{"action":"sample"}'
```

**CSV from curve tracer:**
```bash
CSV=$(cat /path/to/sweeps.csv)
curl -s -X POST http://127.0.0.1:8778/ \
  -H 'Content-Type: application/json' \
  -d "{\"action\":\"plot_csv\",\"device\":{\"id\":\"DUT1\",\"name\":\"My MOSFET\"},\"csv\":$(python3 -c \"import json,sys; print(json.dumps(sys.stdin.read()))\" <<< \"$CSV\"),\"filename\":\"sweeps.csv\"}"
```

**JSON sweeps:**
```json
{
  "action": "plot",
  "device": { "id": "IRF540N-s1", "name": "IRF540N", "type": "NMOS" },
  "sweeps": [
    { "vgs": 4.0, "data": [{ "vds": 0, "id": 0 }, { "vds": 1, "id": 0.25 }, { "vds": 5, "id": 0.5 }] },
    { "vgs": 6.0, "data": [{ "vds": 0, "id": 0 }, { "vds": 1, "id": 1.8 }, { "vds": 5, "id": 4.5 }] }
  ]
}
```

## API Actions (POST / with JSON body)

| Action | Description |
|--------|-------------|
| `plot` | Add device with JSON sweeps |
| `plot_csv` | Add device from curve tracer CSV |
| `overlay` | Add multiple devices at once |
| `sample` | Load built-in demo data |
| `clear` | Clear all data |
| `remove` | Remove device by id |
| `toggle_device` | Toggle device visibility (eyeball) |
| `toggle_sweep` | Toggle individual sweep visibility |
| `compute_saturation` | Compute and show saturation boundary line |
| `clear_saturation` | Hide saturation boundary |
| `set_config` | Change settings (e.g., `{"scale":"log"}`) |
| `analyze` | Extract Vth, Rds(on) from data |

All actions update the frontend in real-time via WebSocket — no page refresh needed.

## CSV Format

The CSV must have column triplets per sweep: `VN (V), IN (A), RN (Ohm)` where N is 1-indexed:

```
V1 (V),I1 (A),R1 (Ohm),V2 (V),I2 (A),R2 (Ohm),...
38.32,0.0009,...
```

Optionally pass `vgs_values: [0, 1, 2, ...]` to label sweeps with their Vgs voltages.

## Real-Time Control

The server has a WebSocket at `ws://127.0.0.1:8778/ws`. Claude can control the visualizer live during demos:

```bash
# Toggle a device's visibility
curl -s -X POST http://127.0.0.1:8778/ -H 'Content-Type: application/json' \
  -d '{"action":"toggle_device","id":"DUT1"}'

# Compute saturation boundary
curl -s -X POST http://127.0.0.1:8778/ -H 'Content-Type: application/json' \
  -d '{"action":"compute_saturation"}'

# Switch to log scale
curl -s -X POST http://127.0.0.1:8778/ -H 'Content-Type: application/json' \
  -d '{"action":"set_config","scale":"log"}'
```

## Shot Log

Monitor API activity: `curl http://127.0.0.1:8778/shotlog?tail=10`

## Example AI Prompts

Users can ask Claude:

- "Plot my MOSFET IV curves from this CSV file"
- "Show me the MOSFET visualizer with sample data"
- "Overlay my BSS138 data on top of the IRF540N"
- "Compute the saturation boundary curve"
- "What's the threshold voltage of this MOSFET?"
- "Switch to log scale to see subthreshold behavior"
- "Export the IV data as CSV"
- "Toggle off sweep 3 so I can focus on the others"
- "Compare these two MOSFETs side by side"

## Keyboard Shortcuts (in the visualizer)

| Key | Action |
|-----|--------|
| L | Toggle linear/log scale |
| K | Compute/clear saturation curve |
| S | Load sample data |
| R | Reset zoom |
| Esc | Clear readout |