This circuit was found in a Popular Electronics from the 90s. The transistors are general purpose, and the gain depends on the ratio between R2 and R1.
This linear bargraph circuit was found in the February 1992 issue of Radio Electronics magazine. The 10...
This interesting circuit, found in a 1984 documentation, captures stations in the FM band and...
This circuit is from an old Signetics documentation. It can be implemented with modern operational...