Found in a 1990 PE Hobbyst, this 4-digit circuit has a high response speed. The circuit is based on TTL logic.
This circuit can use any comparator or even an operational amplifier. We can use the LM339 and the...
This circuit is from an old American amateur radio manual. The circuit shows how to use a Varicap...
This circuit was obtained from the December 1990 issue of Radio Electronics magazine. The circuit...