This circuit is from a 70s documentation. The maximum sampling rate is 800 Hz. The operational amplifier is a common type at the time.
This simple expandable circuit was obtained from a Popular Electronics from the 80's. The supply...
The frequency of the LC resonant circuit must be the same as that of the crystal and the JFET...
This circuit was obtained in a Popular Electronics of 1991. The magazine no longer exists, but the...