Other settings like this can be found on this website. This makes use of old operational amplifiers, as the publication where we obtained, but equivalents can be used.
This configuration has already been used several times in many of our projects and can be found in...
This circuit is from Popular Electronics from October 1981. The diode can also be 1N4004 and the...
This circuit was found in a Radio Electronics Constructor, English magazine of April 1976; The...