Two essential traits of CMOS devices are excessive noise immunity and low static strength consumption. Since one transistor in a MOSFET pair is always off, the series connection consumes a large amount of power momentarily during switching between on and off states. As a result, CMOS devices do not generate as much heat as other forms of logic such as NMOS logic and transistor-transistor logic (TTL). This logic usually has some sustained current even when they are not changing state. These properties allow CMOS to integrate high-density logic functions on a chip. Primarily, for this reason, CMOS has become the most widely used technology implemented on VLSI chips.