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 circuit, which uses an unusual integrated, is from the Motorola Linear Databook of 1990....
This circuit is used to test an inductor (coil) allowing the observation of its opration in an R-L...
This analog to digital converter was obtained from an American documentation from the 90s. Used...