A display device operating in accordance with a sub-field process,
includes a first block which varies the number of bits of a received
image signal, a second block which calculates an average picture level
(APL) of images defined by the image signal transmitted from the first
block, a third block which converts the image signal into sub-field
coding data, and outputs the sub-field coding data to a display panel,
and a fourth block which receives the average picture level from the
second block, converts the received average picture level to the number
of sustaining pulses, transmits the number of sustaining pulses to the
display panel, and transmits the number of sustaining pulses to the third
block, wherein the third block selects the number of bits of a signal to
be input thereinto, in accordance with the number of sustaining pulses
received from the fourth block.