The very high-input impedance of the CMOS gate allows this kind of device to be used as a sensitive touch switch as shown in Figure bellow. This circuit turns on and off with a single touch to the sensor. The 10 M ohm resistor determines the sensitivity and can be altered to function in the range between ’I M ohm and 22 M ohm. The higher the resistor is, the better the sensitivity. The capacitor also can be changed as long as it stays in the range between 0.1 µF and 1 µF depending on the application. Any NAND gate can be used including the Schmitt types, such as the 4093.
Touch Action Switch
