Use of DC Blocking Capacitors

Where are DC-blocking capacitors used?

Where are they used? Can you answer this question? A DC-Blocking Capacitor, often referred to as an AC-coupling capacitor, is a passive electronic device designed to allow alternating current (AC) signals to pass while blocking direct current (DC) components from a circuit.

Why do you need a blocking capacitor?

By preventing the DC voltage from passing, the capacitor ensures that the desired AC signal is preserved. This is especially critical in RF applications where signal clarity is paramount. For example, in a coaxial line, blocking capacitors can be used as inner or outer DC blocks to ensure the clean transmission of RF signals.

Can a capacitor block DC?

Any capacitance can block DC, but a designer should consider the minimum frequency they want to pass when selecting a capacitor value. Finding blocking capacitor solutions for complex real-world electronic systems requires a deep understanding of current flows.

How do I choose the right DC-blocking capacitor?

Choosing the correct DC-blocking capacitor involves considering several factors, including: Capacitance Value: The capacitance determines the cutoff frequency for the signal. A higher capacitance allows lower frequencies to pass, while a lower capacitance blocks them.

Does a DC blocking capacitor affect RF performance?

The impact of the DC blocking capacitor on the performance of RF circuits has been well studied, but not so for its effects during an ESD event.

Why is capacitor C2 a blocking capacitor?

Blocking an unwanted DC voltage occurs because the capacitor acts as an open to the DC voltage, not allowing it to pass through the dielectric. In Figure 2 below, capacitor C2 acts as a blocking capacitor in this voltage divider design with the output waveform around zero volts.