This circuit provides signals in phase with the input and with the phase inverted. The circuit was found in documentation from the 1990s. Transistors are commonly used.
We found this heart rate sensor circuit in a Popular Electronics from the 90s. The placement of...
This circuit, found in an old magazine of the year 1968, uses a Power germanium transistor. This...
This project came out in an article of mine (Newton C. Braga) in the Popular Electronics magazine of...