{
  "spicebook_version": "2026-02-13",
  "metadata": {
    "title": "Common Emitter Amplifier",
    "engine": "ngspice",
    "tags": ["amplifier", "bjt", "intermediate"],
    "created": "2026-02-13T00:00:00Z",
    "modified": "2026-02-13T00:00:00Z"
  },
  "cells": [
    {
      "id": "cell-intro",
      "type": "markdown",
      "source": "# Common Emitter Amplifier\n\nA single-stage BJT amplifier with voltage divider biasing. This is one of the most common amplifier configurations.\n\nKey parameters:\n- **Voltage gain**: approximately -R_C / r_e (inverting)\n- **Input impedance**: R1 || R2 || (beta * r_e)\n- **Bandwidth**: determined by coupling and bypass capacitors",
      "outputs": []
    },
    {
      "id": "cell-ac",
      "type": "spice",
      "source": "Common Emitter Amplifier - Frequency Response\nVCC vcc 0 DC 12\nV1 in 0 AC 1 SIN(0 10m 1k)\n* Bias network\nR1 vcc base 47k\nR2 base 0 10k\n* Transistor (2N2222 model)\nQ1 col base emit QNPN\n.model QNPN NPN(BF=200 IS=1e-14 VAF=100)\n* Collector and emitter resistors\nRC col vcc 4.7k\nRE emit 0 1k\n* Coupling capacitors\nC1 in base 10u\nC2 col out 10u\n* Emitter bypass capacitor\nCE emit 0 100u\n* Load\nRL out 0 10k\n.ac dec 50 10 10meg\n.end",
      "outputs": []
    },
    {
      "id": "cell-explain",
      "type": "markdown",
      "source": "## Frequency Response Analysis\n\nThe Bode plot reveals the amplifier's bandwidth. Look for:\n\n1. **Low-frequency cutoff**: Determined by coupling capacitors C1, C2 and bypass capacitor CE\n2. **Mid-band gain**: The flat region where gain is approximately -R_C / r_e\n3. **High-frequency rolloff**: Due to transistor parasitic capacitances (not modeled here)",
      "outputs": []
    },
    {
      "id": "cell-tran",
      "type": "spice",
      "source": "Common Emitter Amplifier - Transient Response\nVCC vcc 0 DC 12\nV1 in 0 SIN(0 10m 1k)\n* Bias network\nR1 vcc base 47k\nR2 base 0 10k\n* Transistor\nQ1 col base emit QNPN\n.model QNPN NPN(BF=200 IS=1e-14 VAF=100)\n* Collector and emitter resistors\nRC col vcc 4.7k\nRE emit 0 1k\n* Coupling caps\nC1 in base 10u\nC2 col out 10u\nCE emit 0 100u\nRL out 0 10k\n.tran 10u 5m\n.end",
      "outputs": []
    }
  ]
}