# A Voltage Blocking Capacitor

• mmmboh
In summary, the conversation discusses a circuit where changing the DC offset voltage causes channel one to move up and down while channel 2 remains flat. The reason for this is that the capacitor in the circuit blocks the DC current, resulting in no DC voltage across the series resistor and no DC component in channel 2. This is due to the impedance of the capacitor being 1/(wC) at zero frequency.
mmmboh
Hi, I have this circuit:

And when I change the DC offset voltage the wave in channel one moves up and down and the wave in channel 2 doesn't do anything except for flatten out a bit in certain areas (although I'm not sure that's relevant), my question is why? I know channel 2 is the voltage across the resistor, so is the change in DC voltage appearing solely across the capacitor? It appears the capacitor blocks voltage, but why?

Help would be great! :)

The capacitor blocks the DC current. (Its impedance is 1/(wC) so zero frequency means infinite impedance.) No DC current, no DC voltage across the series resistor, the signal in CH2 has no DC component. The DC voltage drops solely across the capacitor, as you said.

ehild

## 1. What is a voltage blocking capacitor?

A voltage blocking capacitor is an electronic component that is used to block or filter out unwanted voltage signals in a circuit. It is also known as a blocking capacitor or a DC blocking capacitor.

## 2. How does a voltage blocking capacitor work?

A voltage blocking capacitor works by allowing only AC signals to pass through while blocking DC signals. It does this by storing electrical charge on its plates and preventing the flow of DC current.

## 3. What are the applications of a voltage blocking capacitor?

A voltage blocking capacitor is commonly used in electronic circuits to isolate AC and DC signals, to improve signal quality, and to protect sensitive components from voltage spikes. It is also used in power supply circuits to filter out unwanted noise.

## 4. How do I choose the right voltage blocking capacitor for my circuit?

The right voltage blocking capacitor for your circuit will depend on factors such as the frequency of the signals, the amount of voltage being blocked, and the size and type of the capacitor. It is important to consult a datasheet or consult with a knowledgeable engineer to select the appropriate capacitor for your specific application.

## 5. Can a voltage blocking capacitor fail or wear out over time?

Yes, like any electronic component, a voltage blocking capacitor can fail or wear out over time. Factors such as high temperatures, excessive voltage, and age can contribute to the degradation or failure of a capacitor. It is important to regularly test and replace capacitors if necessary to ensure proper functionality of your circuit.

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