This circuit was found in 80's Popular Electronics. Transistors are commonly used. The potentiometer R5 adjusts the gain.
This configurable CMOS configuration for frequencies up to a few megahertz was obtained in an...
This circuit is from the 1972 RCA Linear Integrated Circuits Manual, but it can be made based on...
Found in 1980s Electronic Engineering, this circuit uses common phototransistors as sensors. The...