Found in a 1969 Burr-Brown publication, this circuit makes use of integrated components from that period. With modern equivalents, it can be adapted to be used as a shield.
This is the basic configuration of an operational amplifier sample & hold circuit. The FET and...
We found this circuit in Electronics Now magazine from 1996. The frequency is basically given by...
This one-transistor alarm can be used with much more sensors than the two shown by the figure....