The circuit shown in the figure below is from the 1993 Linear Technology Applications. The operational ones used are uncommon and the use of equivalents can be analyzed.
This original 70s RCA circuit appears elsewhere on this site, including original RCA...
This circuit, which makes an astable multivibrator, was found in the March 1973 issue of Radio...
This circuit uses two unijunction transistors and only one capacitor, generating signals at a...