High speed cmos multiplexer having reduced propagation delay

Abstract

A CMOS multiplexing circuit is provided for selecting one of a plurality of input signals under control of a digital select signal for providing an output signal inverted with respect to the selected input signal. A plurality of processing channels one for each input signal and each having exactly first, second, third and fourth transistors serially connected between first and second sources of operating potential are repsonsive to the digital select signal whereby only the second and third transistors in the selected processing channels are enabled. The other processing channels supporting the remaining input signals are disabled. The first and fourth transistors of the selected processing channel are alternately enabled by one of the plurality of input signals for providing the inverse state thereof at the output formed at the interconnection of the second and third transistors. The first and second sources of operating potential need pass through only two transistors which improves the propagation delay and since only the second and third transistors of the selected processing channels are conducting, the transistors forming the remaining non-selected processing channels are effectively removed from the output terminal thereby reducing the capacitive load thereon and improving the propagation delay in the select path.