RC time constant

Charge/discharge curves for a resistor-capacitor pair — time to a percent, or voltage at a moment.

RC time constant τ = R·C: time to charge to a percentage, plus seconds and common percent points.

Charging: V(t) = Vrail·(1−e^(−t/τ)). Runs in this browser.

How to use

  1. Enter resistance and capacitance.
  2. Read τ and 5τ (≈full charge).
  3. Query charge % at a time or time to a %.

What it supports

Ideal RC charge v(t)=V(1−e^(−t/RC)) and discharge V·e^(−t/RC); R 1 mΩ–1 TΩ, C 10 fF–1,000 F, times 0–1e12 s. Leakage and ESR are not modeled.

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