Source line floating circuits, memory devices including the same and methods of reading data in a memory device

A source line floating circuit includes a plurality of floating units. The floating units directly receive decoded row address signals or voltages of word lines as floating control signals, respectively. The decoded row address signals are activated selectively in response to a row address signal. The floating units control electrical connections between source lines and a source voltage in response to the floating control signals in a read operation. Related devices and methods are also described.