ngspice Simulation for typeCAD

Use typeCAD to design your hardware and run simulations with ngspice with the same codebase.

Getting Started

Prerequisites

• a working typeCAD project
• ngspice installed and in your PATH

Installation

Run the following command in your project directory, where your typeCAD package.json file is located:

npm i @typecad/ngspice

Usage

Below is a simple voltage-divider circuit.

import { Schematic, Power } from '@typecad/typecad';
import { Resistor } from '@typecad/passives/0603';
import { ngspiceSimulator } from '@typecad/ngspice';

let typecad = new Schematic('vdiv');
let r1 = new Resistor({ value: '1k', simulation: { include: true } });
let r2 = new Resistor({ value: '1k', simulation: { include: true } });
let vin = new Power({ power: r1.pin(1), gnd: r2.pin(2), voltage: 3.3 });
let ngspice = new ngspiceSimulator(typecad, vin);

typecad.named('in').net(r1.pin(1));
typecad.named('vdiv').net(r1.pin(2), r2.pin(1));
typecad.named('gnd').net(r2.pin(2));

typecad.create(r1, r2);
ngspice.op();

Notes

• The ngspiceSimulator constructor takes a schematic and all power source as parameters, ie. if more than one power source is used, they can all be passed.

let ngspice = new ngspiceSimulator(typecad, battery, regulated_3v3);

• to include a component, fill the simulation property of the component with { include: true }

• ensure the value field contains a valid ngspice expression (no spaces, proper units, etc.).

• only named nets are included in the simulation

  • gnd is a special net in ngspice and is associated with ground or 0

DC Analysis

• to run a DC analysis, call the op method on the simulator

ngspice.op();

The output from the above example is:

🌶️  running ngspice
┌────────────────────┬───────────────┬────────────────────┐
│ Variable           │ Type          │ Value              │
├────────────────────┼───────────────┼────────────────────┤
│ r1:power           │ power         │ 2.7225 mW          │
├────────────────────┼───────────────┼────────────────────┤
│ v(in)              │ voltage       │ 3.3000 V           │
├────────────────────┼───────────────┼────────────────────┤
│ i(r1)              │ current       │ 1.6500 mA          │
├────────────────────┼───────────────┼────────────────────┤
│ i(r2)              │ current       │ 1.6500 mA          │
├────────────────────┼───────────────┼────────────────────┤
│ r2:power           │ power         │ 2.7225 mW          │
├────────────────────┼───────────────┼────────────────────┤
│ i(v1)              │ current       │ -1.6500 mA         │
├────────────────────┼───────────────┼────────────────────┤
│ v(vdiv)            │ voltage       │ 1.6500 V           │
└────────────────────┴───────────────┴────────────────────┘

Each component is listed with its power and current use and each node is listed with its voltage.

Transient Analysis

• To run a transient analysis, call the tran method on the simulator

ngspice.tran('1us', '100ms');

There are additional parameters that can be passed to the tran method and are explained best in the ngspice documentation, section 11.3.10 .TRAN: Transient Analysis.

The output from the above example opens an ngspice plot window for each component and all nodes.