This filter is from a 1977 publication. The circuit employs three 741 or other operational amplifiers. The supply must be symmetrical and the components with (*) are low tolerance.
We found this circuit in an Australian publication from 1991. It is a kit of the time with input...
This time base circuit was found in the January 1988 issue of Radio Electronics magazine. The...
This circuit was found in the December 1983 issue of Radio Electronics magazine. The sensor is an...