What is the primary purpose of a coupling capacitor?

The primary purpose of a coupling capacitor is to block direct current (DC) while allowing alternating current (AC) to pass through. This functionality is crucial in various electronic circuits, especially in audio and radio frequency applications, where it is necessary to isolate different stages of the circuit while still enabling the signal (which is typically AC) to move from one stage to another.

Coupling capacitors are often used in amplifier circuits to couple the output of one stage to the input of another. They prevent DC bias from one stage from affecting the next, thus maintaining the necessary operating conditions for each section of the circuit. By allowing AC signals to pass, they ensure that the desired frequency components of the signal are transmitted, while unwanted DC components are blocked, which can otherwise shift the operating points of the components involved in the circuit.

In this context, while a coupling capacitor does store energy temporarily, that is not its primary purpose. Similarly, while it does block certain currents, the specific function of blocking DC while allowing AC to pass defines its role in circuit design and operation. Therefore, recognizing that the coupling capacitor specifically serves to separate DC from AC in a pathway is key to understanding its application in electronics.