This 1970 Electronic Design circuit uses a varactor or varicap. The circuit divides the frequency of a 150 MHz signal by 2. Similar versions appear on this site.
This circuit is based on a Texas Instruments LinMOS integrated circuit consisting of an...
This sophisticated logic probe for 5 to 12 V circuits (CMOS and TTL) was found in a 1980s...
This 2005 Linear Technology circuit has separate outputs for monitoring the charge and discharge...