We found this measurement circuit with a logarithmic scale in an Electronics Now from November 1995. The circuit uses an integrated component from that time.
This circuit activates a machine to dry hands (fan and heater) when the sensor detects the...
The operational used is like the 741. The circuit is from the datasheet and the formula that...
The second order filter shown in the figure is suggested by Texas Instruments, based on the TL081...