Generally, it is a parallel plate capacitor and its construction is extremely easy. In between the parallel plates of this capacitor, a dielectric material is used. So this capacitor plays a key role while getting final output like AC signals. Coupling capacitors are mainly used in analog circuits whereas the decoupling. Whenever a capacitor is selected for coupling applications, there are some key parameters that need to consider like series resonant frequency,. The coupling capacitor applications include the following. 1. This capacitor is used in audio circuits 2. This capacitor is used in many circuits where the AC signal is desired as output signal while DC signal is just used for certain. 1). What is the coupling capacitor? A capacitor that is used to connect the AC signal from one circuit to another is known as a coupling capacitor. 2). What are the capacitors used in coupling applications? They are aluminum.