| This article describes a very basic BFO detector which
uses only two transistors and an LM389 audio amplifier. The
LM389, in fact, contains the two transistors that form the
search and reference oscillators so the whole circuit is
comprised of a single IC and a handful of discrete linear
components. Accurately matched transistors are not really
necessary in the oscillators so you can use discrete
transistors and an LM386 audio amp instead of the LM389.
This article was published in the "Design
Ideas" section of the December 18, 1997 issue of EDN,
a popular electronics trade magazine that offers free
subscriptions to qualifying individuals. |