duplicates de frequency
Fin = 1KHz , Fout = 2kHz
Only when the Red and Blue waves are both high or low. The XNOR gate returns high. That means that the output pulse is high on the
falling and reaching edge, so the output is a double freq wave (not a square wave).
The amp is to get 5V of amplitude at the output.
It works with any freq, but bigger freqs means shorter output pulse (1% HIGH and 99% LOW, for example). Consider low for voltages under 2.5V.
