Core formulas
| Q = C V | Charge on plates |
|---|---|
| I = C · dV/dt | Current from changing voltage |
| E = ½ C V² | Energy stored (joules) |
| X_C = 1 / (2π f C) | Capacitive reactance (Ω) |
| τ = R · C | Time constant (seconds) |
| V(t) = V₀ (1 − e^{-t/τ}) | Charging through R |
| f_c = 1 / (2π R C) | RC filter −3 dB corner |
Combinations
| C parallel | C_total = C1 + C2 + … (capacitance adds like resistor parallel) |
|---|---|
| C series | 1 / C_total = 1/C1 + 1/C2 + … (voltages add) |
| Two in series | C = (C1 · C2) / (C1 + C2) |
SMD 3-digit code
| Code | Value |
|---|---|
| 100 | 10 × 10⁰ pF = 10 pF |
| 101 | 10 × 10¹ pF = 100 pF |
| 102 | 10 × 10² pF = 1 000 pF = 1 nF |
| 103 | 10 × 10³ pF = 10 nF |
| 104 | 10 × 10⁴ pF = 100 nF |
| 105 | 10 × 10⁵ pF = 1 µF |
| 106 | 10 × 10⁶ pF = 10 µF |
| 473 | 47 × 10³ pF = 47 nF |
| 224 | 22 × 10⁴ pF = 220 nF |
Prefix shorthand
| "n47" or "470n" | 470 nF / 0.47 µF |
|---|---|
| "4µ7" or "4u7" | 4.7 µF |
| "p47" | 0.47 pF |
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