The operational amplifier and the sensor used in this National Semiconductor circuit are not common today, but the configuration can be adapted to use current components.
We found this circuit in a publication about operational in the 90s. The circuit is based on the...
This filter with Butterworth response makes use of operational amplifiers 741 or equivalent and...
This circuit was found in a publication in the 1950s, mainly applying to germanium transistors of the...