hehe, as far as i know ,the cell_rising and falling transition time of clock buffer is almost equal, but the normal buffer not. so we can get duty cycle of clock.
Clock buffers are specially designed buffers used for clock tree synthesis and clock routing. These buffers have equal rise and fall times so that both the clock edges have same slope and are equal. These buffers also have low delay and lesser parasitic capacitance so that the next buffer or logic does not load the buffer and cause the clock waveform slope to change.
clock buffer are ideal for CTS !! specially designed to hav same rise n fall time ..
hence used in clock tree n more over sometimes normal buffers or inverters r used in CTS