This humidity sensor indicates the different levels of conduction of the sensors through an LED bar. The circuit is from Popular Electronics and must be powered by cells or battery.
This is the basic configuration of an operational amplifier sample & hold circuit. The FET and...
The integrated circuit 4136 consists of operational amplifiers of type 741 in the same enclosure and...
We find this circuit in a 1987 publication. It makes use of comparators constructed around the 741...