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Ternary and Quaternary CNTFET Full Adders are less efficient than the Binary Ones for Carry-Propagate Adders

In Carry Propagate Adders, carry propagation is the critical delay. The most efficient scheme is to generate Cout0 (Cin=0) and Cout1(Cin=1) and multiplex the correct output according to Cin. For any radix, the carry output is always 0/1. We present two versions of ternary adders with Cin = (0V, Vdd/2) and Cin = (0V, Vdd) and two versions of quaternary adders with Cin = (0V, Vdd/3) and Cin = (0V, Vdd). Using full swing Vdd for Cin reduces the propagation delays for ternary and quaternary adders. 6-bit, 4-trit and 3-quit CPAs are then compared.