Floating

Definition

1. A signal line is said to be "floating" if it is not connected to any voltage supply, ground, or ground-referenced signal source.

   Examples:

   • An open-drain, high-impedance (hi-z) output when in the off (hi-z) mode
   • In microcomputer systems, a data or address bus may, at times, be undriven (floating). This is permissible because control signals indicate when data is valid, so users of the bus know when the signal can be ignored.

2. One form of non-volatile memory device is achieved via floating gates. The gate of a MOSFET has no connection, allowing charge to remain indefinitely. The gate charge is changed using Fowler-Nordheim tunneling or hot-carrier injection. EPROM, EEPROM, and flash memory are examples.