B. Filter RC

After studying the low pass RC filter, there is now another RC circuit to be used as a high pass filter by connecting R and C in the series but the output voltage is the end of the resistor as illustrated below.

For high pass filters produced by RC differentiator circuits, the output signal is a differential of the input signal stated by:

With the Vo / Vi ratio or the voltage strengthening factor (AV) of the circuit of:

When a special frequency where XC = R, the amplitude becomes: 

A critical frequency or a cut-off frequency of: 

The normalized plot between the AV voltage strengthening factor and frequency f produces a curve as shown in the following figure.