Design and Performance Analysis of hybrid adders for high speed arithmetic circuit

Abstract: Adder cells using Gate Diffusion Technique (GDI) & PTL-GDI technique are described in this paper. GDI technique allows reducing power consumption, propagation delay and low PDP (power delay product) whereas Pass Transistor Logic (PTL) reduces the count of transistors used to make different logic gates, by eliminating redundant transistors. Performance comparison with various Hybrid Adder is been presented. In this paper, we propose two new designs based on GDI & PTL techniques, which is found to be much more power efficient in comparison with existing design technique. Only 10 transistors are used to implement the SUM & CARRY function for both the designs. The SUM and CARRY cell are implemented in a cascaded way i.e. firstly the XOR cell is implemented and then using XOR as input SUM as well as CARRY cell is implemented. For Proposed GDI adder the SUM as well as CARRY cell is designed using GDI technique. On the other hand in Proposed PTL-GDI adder the SUM cell is constructed using PTL technique and the CARRY cell is designed using GDI technique. The advantages of both the designs are discussed. The significance of these designs is substantiated by the simulation results obtained from Cadence Virtuoso 180nm environment.