Separating DC & AC components

A capacitor does not allow DC to pass through it. This property can be demonstrated using a squarewave swinging from 0 to 5V.



Separate the AC component of a 0 to 5V sqauarewave.




The observed waveforms with and without the series capacitor are shown in figure. The voltage is swinging between 0 and 5 volts. After passing through the capacitor the voltage swings from -2.5 volts to +2.5 volts.

What will you get if you subtract a 2.5 from the y-coordinate of every point of the first graph? That is what the capacitor did. It did not allow the DC part to pass through. This original square wave can be considered as a 2.5V AC superimposed on a 2.5V DC.

In case the output on A2 is having a DC component, connect a 100kΩ resistor from A2 to GND.