velxio/frontend/src/__tests__/spice-active.test.ts

import { describe, it, expect } from 'vitest';
import { runNetlist } from './helpers/testSolver';

describe('ngspice — diode', () => {
  it('1N4148-style diode forward drop is 0.55–0.80V @ ~4 mA', { timeout: 30_000 }, async () => {
    const netlist = `Diode forward
V1 vcc 0 DC 5
R1 vcc a 1k
D1 a 0 DMOD
.model DMOD D(Is=2.52n N=1.752 Rs=0.568 Ibv=0.1u Bv=100)
.op
.end`;
    const { dcValue } = await runNetlist(netlist);
    const Va = dcValue('v(a)');
    expect(Va).toBeGreaterThan(0.55);
    expect(Va).toBeLessThan(0.8);
  });

  it('full-wave bridge rectifier outputs ~|Vin| − 2·Vf', { timeout: 30_000 }, async () => {
    const netlist = `Bridge rectifier
V1 a b SIN(0 6 50)
D1 a p DMOD
D2 b p DMOD
D3 n a DMOD
D4 n b DMOD
R1 p n 1k
.model DMOD D(Is=1e-14 N=1)
.tran 0.1m 40m
.end`;
    const { vec } = await runNetlist(netlist);
    const t = vec('time') as number[];
    const vp = vec('v(p)') as number[];
    const vn = vec('v(n)') as number[];
    let peakOut = -Infinity;
    let minOut = Infinity;
    for (let i = 0; i < t.length; i++) {
      if (t[i] < 20e-3) continue;
      const d = vp[i] - vn[i];
      if (d > peakOut) peakOut = d;
      if (d < minOut) minOut = d;
    }
    expect(peakOut).toBeGreaterThan(4.2);
    expect(peakOut).toBeLessThan(5.4);
    expect(minOut).toBeGreaterThan(-0.1);
  });
});

describe('ngspice — BJT', () => {
  it(
    'common-emitter amplifier inverts and amplifies a small signal',
    { timeout: 30_000 },
    async () => {
      const netlist = `Common-emitter
Vcc vcc 0 DC 12
Vin in 0 SIN(0 0.01 1k)
Cin in b 1u
RB1 vcc b 47k
RB2 b 0 10k
RC vcc c 4.7k
RE e 0 1k
CE e 0 100u
Q1 c b e Q2N2222
Cout c out 1u
Rout out 0 100k
.model Q2N2222 NPN(Is=1e-14 Bf=200 Vaf=75)
.tran 10u 6m
.end`;
      const { vec } = await runNetlist(netlist);
      const t = vec('time') as number[];
      const vin = vec('v(in)') as number[];
      const vout = vec('v(out)') as number[];
      let maxIn = 0;
      let maxOut = 0;
      let minOut = Infinity;
      for (let i = 0; i < t.length; i++) {
        if (t[i] < 3e-3) continue;
        if (Math.abs(vin[i]) > maxIn) maxIn = Math.abs(vin[i]);
        if (vout[i] > maxOut) maxOut = vout[i];
        if (vout[i] < minOut) minOut = vout[i];
      }
      const gain = (maxOut - minOut) / (2 * maxIn);
      expect(gain).toBeGreaterThan(30);
    },
  );
});

describe('ngspice — MOSFET', () => {
  it('N-MOS switch: V_GS > Vth pulls drain to ground', { timeout: 30_000 }, async () => {
    const netlist = `N-MOS switch
Vcc vcc 0 DC 5
Vgate gate 0 DC 5
RL vcc drain 1k
M1 drain gate 0 0 NMOS_L1 L=1u W=100u
.model NMOS_L1 NMOS(Level=1 Vto=1.0 Kp=50u Lambda=0.01)
.op
.end`;
    const { dcValue } = await runNetlist(netlist);
    expect(dcValue('v(drain)')).toBeLessThan(1.0);
  });

  it('N-MOS switch: V_GS < Vth leaves drain near V_dd', { timeout: 30_000 }, async () => {
    const netlist = `N-MOS off
Vcc vcc 0 DC 5
Vgate gate 0 DC 0
RL vcc drain 1k
M1 drain gate 0 0 NMOS_L1 L=1u W=100u
.model NMOS_L1 NMOS(Level=1 Vto=1.0 Kp=50u Lambda=0.01)
.op
.end`;
    const { dcValue } = await runNetlist(netlist);
    expect(dcValue('v(drain)')).toBeGreaterThan(4.9);
  });
});

describe('ngspice — op-amp (behavioral E-source)', () => {
  it('inverting amplifier: V_out = −(R_f/R_in) · V_in', { timeout: 30_000 }, async () => {
    const netlist = `Inverting amp
Vin in 0 DC 0.2
Rin in n 1k
Rf n out 10k
Eopa out 0 0 n 1e6
.op
.end`;
    const { dcValue } = await runNetlist(netlist);
    expect(dcValue('v(out)')).toBeCloseTo(-2.0, 2);
  });
});