A 1.67 GHz 32-bit pipelined carry-select adder using the complementary scheme

Using a carry-select adder scheme, an adder with small number of stages can operate as fast as an adder with large number of stages. In this paper, a 4-block 5-stage 32-bit pipelined carry-select adder is designed and implemented. The proposed adder operates as fast as a conventional 16-stage 32-bit pipelined ripple-carry adder while the number of registers required is nearly same as a conventional 4-stage pipelined adder. This adder is operated at 1.67 GHz clock frequency in a standard 0.25 μm CMOS technology with 2.5 V supply voltage.