I use this one here: http://www.amazon.com/gp/product/B0015YRMXI/ref=oh_details_o00_s00_i00

The general rule is if a splitter has an external power source, there is no lag. Hell this thing actually cuts lag as it stops the TV from performing any post processing 9the main cause of lag)

(1 input into two outputs = splitter. Two inputs into one output = switch/switcher)