Using Expressions for Component Values

Tscircuit lets you use normal JavaScript expressions to calculate component values. This is useful when a part's value depends on other parameters, like setting a voltage divider's output or picking the capacitor for an LC resonant circuit.

Voltage divider

Here we pick R2 so that a divider powered from vin produces vout. Changing any of the parameters automatically recomputes R2.

export default () => {
const vin = 5
const vout = 3.3
const r1 = 1e3
const r2 = r1 * (vout / (vin - vout))
return (
  <board>
    <voltagesource
      name="V1"
      voltage={vin}
      connections={{ pin1: "net.VCC", pin2: "net.GND" }}
    />
    <resistor
      name="R1"
      resistance={r1}
      connections={{ pin1: "net.VCC", pin2: "net.OUT" }}
    />
    <resistor
      name="R2"
      resistance={r2}
      connections={{ pin1: "net.OUT", pin2: "net.GND" }}
    />
  </board>
)
}

LC resonant circuit

The resonant frequency of an LC tank is f = 1/(2π√(LC)). Knowing the desired frequency and an inductance, we can compute the required capacitance.

export default () => {
const f = 1e6 // 1 MHz
const L = 10e-6 // 10 µH
const C = 1 / ((2 * Math.PI * f) ** 2 * L)
return (
  <board>
    <inductor
      name="L1"
      inductance={L}
      connections={{ pin1: "net.IN", pin2: "net.OUT" }}
    />
    <capacitor
      name="C1"
      capacitance={C}
      connections={{ pin1: "net.OUT", pin2: "net.GND" }}
    />
  </board>
)
}

These examples show how expressions make it easy to drive component values from formulas so designs can adapt when requirements change.