This circuit was found in 80's Popular Electronics. Transistors are commonly used. The potentiometer R5 adjusts the gain.
Indicated for scanning circuit applications, we found this generator in a Radio Electronics from the 80s....
This circuit tests crystals up to a few megahertz with ease. The circuit is from a 1977...
Found in documentation from the 70s, this circuit uses an operational one from that time. It goes for...