Chapter 2

Subthreshold Source-Coupled Logic

Armin Tajalli and Yusuf Leblebici

Microelectronic Systems Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland

2.1 Introduction

Without any doubt, energy dissipation is one of the major concerns of our modern world. In integrated systems, regardless of operating conditions, this parameter plays a very critical rule in any kind of design. Generally, there is a tight tradeoff between performance of a system and its energy consumption and power efficiency. The power efficiency can be measured by amount of energy that needs to be dissipated to achieve a specific performance level:

(2.1) equation

Based on this definition of figure of merit (FOM), different designs can be categorized in different levels of energy efficiency such as energy-efficient, low energy (low power), and ultralow energy (ultralow power). Energy efficiency or equivalently FOM depends on many different parameters 43 and generally a very careful design approach is required to obtain an optimized result.

  • Fabrication technology: Generally technology scaling provides faster transistors with less parasitic effects which helps to improve the energy efficiency of a system. Unfortunately, this sentence is not always correct. For example, by technology scaling different sources of leakage current aggregate the static power dissipation of a system which translates ...

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