This circuit has a sensitivity of 2uW. We found it in documentation from the 1980s. The integrated circuit is from that time. Equivalents can be tried.
This circuit can be found on this website in similar versions. The power supply is given in...
We found this third-order Butterworth asymmetric filter in an old manufacturer documentation. The...
This circuit was found in a Japanese documentation of the 70's. It uses transistors of the era and is...