freechips/fullcustom/fullcustom-transistor.ipynb

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   "source": [
    "# Fullcustom analog design demo using Magic"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The environment path must be retrieved in order to provide _Magic_ with the technology files."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "id": "ghmpRJhL3ac3"
   },
   "outputs": [],
   "source": [
    "import os\n",
    "CONDA_PREFIX = os.environ['CONDA_PREFIX']"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "id": "CQdALyHZ9Z01"
   },
   "source": [
    "## Sources"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Graphic Design System file (GDS)\n",
    "\n",
    "A GDS file is drawn by hand:"
   ]
  },
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   "source": [
    "%%script magic -dnull -noconsole -rcfile {CONDA_PREFIX}/share/pdk/sky130A/libs.tech/magic/sky130A.magicrc\n",
    "cellname rename (UNNAMED) mosfet\n",
    "\n",
    "box 0 0 950nm 650nm\n",
    "paint ndiffusion\n",
    "\n",
    "box 400nm -600nm 550nm 1200nm\n",
    "paint polysilicon\n",
    "\n",
    "box 0 0 400nm 650nm\n",
    "label source\n",
    "port make 3\n",
    "\n",
    "box 550nm 0 950nm 650nm\n",
    "label drain\n",
    "port make 1\n",
    "\n",
    "box 400nm -600nm 550nm 0\n",
    "label gate\n",
    "port make 2\n",
    "\n",
    "extract\n",
    "ext2spice lvs\n",
    "ext2spice cthresh 0\n",
    "ext2spice\n",
    "\n",
    "gds labels no\n",
    "gds write mosfet.gds"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Display layout\n",
    "\n",
    "The implemented layout can be retrieved as follows:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
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   "source": [
    "import gdstk\n",
    "import IPython.display\n",
    "\n",
    "library = gdstk.read_gds('mosfet.gds')\n",
    "top_cells = library.top_level()\n",
    "top_cells[0].write_svg('mosfet.svg', scaling=200)\n",
    "IPython.display.SVG('mosfet.svg')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "id": "YZdXQnCJ9h_o"
   },
   "source": [
    "## Simulation"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### PySPICE"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "_PySPICE_ is used for analog simulation of the circuit."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
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    },
    "id": "9scIFl1w7Lk6",
    "outputId": "47f12782-4e69-471f-8101-6abfdc041a28"
   },
   "outputs": [],
   "source": [
    "from PySpice.Spice.Netlist import Circuit, SubCircuit, SubCircuitFactory\n",
    "from PySpice.Unit import *\n",
    "import matplotlib.pyplot as plt\n",
    "\n",
    "circuit = Circuit('mosfet0')\n",
    "circuit.lib(f'{CONDA_PREFIX}/share/pdk/sky130A/libs.tech/ngspice/sky130.lib.spice', 'tt')\n",
    "circuit.include('mosfet.spice')\n",
    "circuit.X('mosfet0', 'mosfet', 'DRAIN', 'GATE', 'VGND')\n",
    "circuit.V('gnd', 'VGND', 0, 0)\n",
    "circuit.V('dd', 'VPWR', 'VGND', 1.8)\n",
    "circuit.R('', 'VPWR', 'DRAIN', '10k')\n",
    "circuit.PulseVoltageSource('Vin', 'GATE', 'VGND',\n",
    "                           initial_value=0@u_V, pulsed_value=1.8@u_V,\n",
    "                           rise_time=10@u_ps, fall_time=10@u_ps,\n",
    "                           pulse_width=1@u_ns, period=2@u_ns, delay_time=1@u_ns)\n",
    "simulator = circuit.simulator()\n",
    "analysis = simulator.transient(step_time=10@u_ps, end_time=2@u_ns)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Plot the waveform"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The output waveform can be plotted:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "scrolled": false
   },
   "outputs": [],
   "source": [
    "fig, ax = plt.subplots(figsize=(20, 10))\n",
    "ax.set_title('mosfet')\n",
    "ax.set_xlabel('time in 1e-14s')\n",
    "ax.set_ylabel('voltage in V')\n",
    "ax.plot(analysis.GATE)\n",
    "ax.plot(analysis.DRAIN)\n",
    "ax.legend(('GATE', 'DRAIN'))\n",
    "plt.tight_layout()\n",
    "plt.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# References\n",
    "Inspired from:\n",
    "“Silicon Notebooks.” CHIPS Alliance, Apr. 08, 2023. Accessed: Apr. 10, 2023. [Online]. Available: https://github.com/chipsalliance/silicon-notebooks/blob/b65134a43b01ae31423f7ee87110740b2257ac42/analog-inverter-magic.ipynb (Apache License 2.0)"
   ]
  }
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