This circuit is designed to measure very weak currents, in the order of picoamperes. We found it in an American documentation from the 80s. The integrated circuit is from that time.
November 2016 - The TL3780 ultra-miniature E-switch touch switches can now be obtained from Mouser...
Using a 4046 PLL this circuit was obtained from the October 1994 issue of Electronics Now...
Found in a 1968 US publication, it is a font filter. The transistor is according to the desired...