Low-Power Logic Styles: CMOS Versus Pass-Transistor Logic

Recently reported logic style comparisons based on full-adder circuits claimed complementary pass-transistor logic (CPL) to be much more power-efficient than complementary CMOS. However, new comparisons performed on more efficient CMOS circuit realizations and a wider range of different logic cells, as well as the use of realistic circuit arrangements demonstrate CMOS to be superior to CPL in most cases with respect to speed, area, power dissipation, and power-delay products. An implemented 32-b adder using complementary CMOS has a power-delay product of less than half that of the CPL version. Robustness with respect to voltage scaling and transistor sizing, as well as generality and ease-of-use, are additional advantages of CMOS logic gates, especially when cell-based design and logic synthesis are targeted. This paper shows that complementary CMOS is the logic style of choice for the implementation of arbitrary combinational circuits if low voltage, low power, and small power-delay products are of concern.