This circuit was found in a documentation of the 80s, having didactic purpose. For R1 values between 10k to 1M can be used. Transistors are general purpose types.
This circuit is from 1992 documentation. The operational circuit, which is uncommon nowadays, can...
The circuit suggested in the figure differentiates the signal from the negative front of a...
Suitable for the medium wave band with a loop antenna, this receiver was published in Radio...