RC,RE,RB1,RB2 calculator for Class A NPN Common-Emitter Amplifier

Main.scala

import scala.collection.mutable

// RC,RE,RB1,RB2 calculator for Class A NPN Common-Emitter Amplifier
object Main {
  
  val I_DIVIDER_GAIN = 10 // I0 > IB

  def main(args: Array[String]): Unit = {
    val Vcc = 19.5
    val inputs = List(
      Input(label = "2N3904", vcc = Vcc, hfe = 100, vbe = 0.7, icq = 0.001, ve = 2),
      Input(label = "TIP122", vcc = Vcc, hfe = 1000, vbe = 1.2, icq = 0.1, ve = 2),
    )

    inputs.foreach { in =>
      val r = calc(in)
      println("Input:")
      println(in)
      println("Result:")
      println(r)
      println("=" * 10)
    }

  }

  /*

  A current I0 goes through resistors R1 and R2 and a current Ib just goes through R1 and enters the base
  from the connection with R1 and R2. Conservation of current allows us to conclude the current in R1 is
  the sum of these currents that is (I0 + Ib).

  */

  /*
  +---[ R1 ]---+---[ R2 ]---+
  |            |            |
  I0+Ib        Ib           I0
  |            |            |
  +------------+------------+
               |
             V_battery
               -
   */


  def calc(input: Input): Result = {
    val ic = input.icq
    val ib = input.icq / input.hfe


    val vrc = input.vcc / 2
    val vb = input.vbe + input.ve

    val re: Int = (input.ve / input.icq).intValue
    val rc: Int = (vrc / ic).intValue

    // bias voltage divider

    // (I0+IB)*R1 + I0*R2 = VCC
    // VBE+VE = I0*R2
    // (I0+Ib)*R1 + (VBE+VE) = VCC
    // VB = VBE+VE
    // (I0+IB)*R1 + VB = VCC
    // (I0+IB)*R1 = VCC-VB
    // I0 = I_DIVIDER_GAIN * IB
    // R1 = (VCC-VB) / (I0+IB)
    // neglect IB since IB << I0
    // R1 = (VCC-VB) / I0
    val i_divider = I_DIVIDER_GAIN * ib // I0
    val rb1: Int = ((input.vcc - vb) / i_divider).intValue
    // VBE+VE = I0*R2
    // VB = I0*R2
    // R2 = VB / I0
    val rb2: Int = (vb / i_divider).intValue

    Result(
      vb = vb,
      re = re,
      rc = rc,
      rb1 = rb1,
      rb2 = rb2
    )

  }

  /**
   *
   * @param label some information
   * @param vcc   power source (V)
   * @param hfe   transistor gain (100-1000)
   * @param vbe   base-emitter voltage (V)
   * @param icq   quiescent current (A)
   * @param ve    emitter voltage, 10% of vcc (V)
   */
  case class Input(label: String,
                   vcc: Double,
                   hfe: Int,
                   vbe: Double,
                   icq: Double,
                   ve: Double) {
    override def toString: String = {
      val sb = new mutable.StringBuilder()
      sb.append("LABEL=").append(label).append("\n")
      sb.append("VCC=").append(vcc).append("\n")
      sb.append("hFE=").append(hfe).append("\n")
      sb.append("VBE=").append(vbe).append("\n")
      sb.append("ICQ=").append(icq).append(" A\n")
      sb.append("VE=").append(ve).append("\n")
      sb.toString()
    }
  }

  /**
   *
   * @param vb  base voltage
   * @param re  emitter resister
   * @param rc  collector resister
   * @param rb1 voltage divider resister 1
   * @param rb2 voltage divider resister 2
   */
  case class Result(vb: Double,
                    re: Int,
                    rc: Int,
                    rb1: Int,
                    rb2: Int) {
    override def toString: String = {
      val sb = new mutable.StringBuilder()
      sb.append("VB=").append(vb).append("\n")
      sb.append("RE=").append(re).append("\n")
      sb.append("RC=").append(rc).append("\n")
      sb.append("RB1=").append(rb1).append("\n")
      sb.append("RB2=").append(rb2).append("\n")
      sb.toString()
    }
  }
}