The following example is taken from The Arts of Electronics book which illustrates what a blocking capacitor does in easy manner. A DC blocking capacitor blocks the DC component of an ac signal but couples the ac part of the signal. The circuit example and simulation is done using multisim online software.

Following is an example circuit to illustrate the application of blocking capacitor. A 2V peak, 1KHz signal ac signal is applied to a simple voltage divider circuit via the blocking capacitor C1 of capacitance 4.7uF. The voltage at the node labelled output is at 5V dc.

When the input ac signal is applied, the 1KHz signal ac signal rides on the 5V dc signal. We can see this using an oscilloscope connected at this node.

Now running the simulation we get the following graph from the oscilloscope.

 If we want we can get rid of the 5V dc to get pure ac signal at the output by attaching another blocking capacitor C2 and a load resistor.

Now we can view the waveform at the output from the second stage circuit using an oscilloscope.

Then from the oscilloscope we can see how the waveform of the signal looks like.

As you can see the 5V dc signal is blocked by the second stage DC blocking capacitor C2 and we get a clean ac signal at the output.


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