Using an operational amplifier of the time, this circuit was obtained from a 90s Radio Electronics. The circuit covers the frequency range from 2 Hz to 20 kHz.
The CMOS 4046 integrated circuit is not very common today, consisting of a very efficient PLL for...
This circuit can also use other series operational amplifiers such as MC33172, MC33174, MC35171,...
This circuit is intended to verify the maximum frequency of blinks that a person can detect....