This is a low-gain amplifier to operate as a booster. We found it in an American documentation from 1947. The circuit uses a coupling transformer at the input.
This low-noise, low-drift amplifier was found in a 90's EDN. It can be implemented with modern...
Using a CMOS 4001, this circuit provides frequency readings on an analog instrument. The idea of...
This analog frequency meter for low frequencies was found in Radio Electronics magazine from July...