Found in a Philips' 1968 documentation, this circuit is slightly different from the previous one. The components are also from the era, and modern equivalents can be used.
We have in the figure a traditional amplifier configuration with operational amplifier. The source...
This circuit was found in a 1977 Radio Shack documentation. The circuit is TTL, which must be...
This circuit is suitable for modulating small FM transmitters for eavesdropping or espionage. The...