Step-by-step method
- Always check units, prefixes and order of magnitude.
- Calculate cutoff frequency, time constant and attenuation for a first-order RC filter.
- Compare the result with temperature, tolerances and real conditions.
RC filter cutoff frequency
Calculate cutoff frequency, time constant and attenuation for a first-order RC filter.
Calculate
Cutoff frequency
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Time constant
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Reactance at fc
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Response at test frequency
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Mistakes to avoid
- Always check units, prefixes and order of magnitude.
- Do not use an ideal result without margin or a datasheet check.
- Compare the result with temperature, tolerances and real conditions.
Component selection
Choose suitable resistor and capacitor tolerances and verify the real cutoff with available values.
Worked example
With 10 kΩ and 100 nF, fc is about 159 Hz and the signal is −3.01 dB at cutoff.
Limits and safety
Source and load impedance alter the response; use a buffer when either is not negligible.
Technical sources
Do not use an ideal result without margin or a datasheet check.