---
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). Also use when installing the MOSFET visualizer. 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", "install mosfet visualizer".
---

# 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.

**Source:** https://github.com/adom-inc/mosfet-visualizer
**Port:** 8778

## Installation

Run this block to install or update. It's idempotent — safe to run multiple times.

```bash
INSTALL_DIR="/home/adom/mosfet-visualizer"

if [ -d "$INSTALL_DIR/.git" ]; then
  echo "[mosfet-visualizer] Updating..."
  cd "$INSTALL_DIR" && git pull origin main 2>&1
else
  echo "[mosfet-visualizer] Installing..."
  git clone https://github.com/adom-inc/mosfet-visualizer.git "$INSTALL_DIR" 2>&1
fi

cd "$INSTALL_DIR" && npm install --production 2>&1 | tail -3

# Start the server (idempotent)
bash "$INSTALL_DIR/start-mosfet-visualizer.sh"
```

## Verify Installation

```bash
curl -sf http://127.0.0.1:8778/health && echo " OK" || echo " NOT RUNNING"
```

## Open the Visualizer

Open a Web View tab pointing to `/proxy/8778/viz`:

```bash
# Get a leaf pane ID
PANE_ID=$(adom-cli hydrogen workspace get 2>/dev/null | python3 -c "
import json,sys
layout = json.load(sys.stdin)
def find_leaf(node):
    if node.get('type') == 'leaf': return node['id']
    if node.get('type') == 'split': return find_leaf(node.get('second', node.get('first', {})))
    return None
print(find_leaf(layout['root']))
")

PROXY_BASE=$(echo "$VSCODE_PROXY_URI" | sed 's|{{port}}.*||')

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}8778/viz\"}"
```

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

**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 }] }
  ]
}
```

## 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

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:

```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

- "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"
- "Install the MOSFET IV visualizer"

## Keyboard Shortcuts

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

## Updating

```bash
cd /home/adom/mosfet-visualizer && git pull origin main && npm install --production
# Restart: kill old process, start new
pkill -f 'node.*mosfet-visualizer.*server.js' 2>/dev/null; bash start-mosfet-visualizer.sh
```