This high input impedance circuit is suggested by Motorola's 1993 Linear Interface ICs. The power supply must be symmetrical. The circuit has a differential input.
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...