Arrangements of R and C

Author: N.H. Crowhurst

RC circuit with C in series. When the capacitor is in series, low frequency voltages are blocked but audio frequencies pass.

The effect of this frequency discrimination of resistance and capacitance in the same circuit depends on the way the components are used. If the capacitance is in series with the audio signal, it will tend to stop the low frequencies, blocking d-c altogether and losing most of the voltages at the extremely low frequencies. At high frequencies, all of the audio voltage will be transferred through the capacitor. The coupling capacitor between stages of amplification used is in this position of capacitance, which means that it produces a loss of low-frequency response.

On the other hand, if the capacitance is in shunt, or so that the audio signal at the output of the arrangement appears across the capacitance, then its presence will mean that high frequencies almost disappear.

RC circuit with C in shunt. When capacitance is in shunt, low-frequency audio components are in the output, but high-frequency components are bypassed.