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RC
Time Constant
τ = R × C · Charge/Discharge · Frequency · Component Selection
Time Constant
Frequency
Find Component
Resistance (R)
*
Ohms (Ω)
Capacitance (C)
*
Farads (F)
Time Constant (τ)
Seconds (s)
R=1kΩ, C=1µF
R=10kΩ, C=100nF
R=100kΩ, C=10nF
Calculate
—
s
Time constant (τ)
τ = R × C
Time Constant (τ)
—
s
63% Charge
—
s
95% Charge (3τ)
—
s
99% Charge (5τ)
—
s
Cutoff Freq (fc)
—
Hz
RC Product
—
s
Voltage
Time (τ)
Exponential Charge Curve
1τ
3τ
5τ
Resistance (R)
*
Ohms (Ω)
Capacitance (C)
*
Farads (F)
Cutoff Frequency (fc)
Hertz (Hz)
R=1kΩ, C=1µF
R=10kΩ, C=100nF
Calculate
—
Hz
Cutoff frequency
fc = 1/(2πRC)
Cutoff Freq (fc)
—
Hz
Time Constant (τ)
—
s
Angular Freq (ω)
—
rad/s
Phase Shift @ fc
-45°
Gain (dB)
Frequency (Hz)
fc
-3dB point
Time Constant (τ)
*
Seconds (s)
Resistance (R)
*
Ohms (Ω)
τ=1ms, R=1kΩ
τ=10ms, R=10kΩ
τ=100µs, R=1kΩ
Find C
—
F
Required capacitance
C = τ / R
Calculated C
—
F
Suggested (E24)
—
F
E24
Cutoff Freq
—
Hz
RC Product
—
s