Capacitive coupling

This technique helps to isolate the DC bias settings of the two coupled circuits.

A coupling capacitor's ability to prevent a DC load from interfering with an AC source is particularly useful in Class A amplifier circuits by preventing a 0 volt input being passed to a transistor with additional resistor biasing; creating continuous amplification.

However, if a signal passing through the coupling capacitance has a frequency that is low relative to the RC cutoff frequency, voltages can develop across the capacitor, which for some capacitor types results in changes of capacitance, leading to distortion.

A gimmick loop is a simple type of capacitive coupler: two closely spaced strands of wire.

If a high-gain amplifier's output capacitively couples to its input it may become an electronic oscillator.