Many modern CMOS gate circuits are buffered with additional transistor stages on their outputs. For example, an unbuffered AND gate is shown here, with no more transistors than is necessary to fulfill the AND logic function:



One type of buffered CMOS AND gate looks like this:



As far as the basic logic function is concerned, the additional transistors are unnecessary. However, the buffering they provide does serve a useful function. What is that function? Are there any disadvantages to buffered logic gates, versus unbuffered?