Impact of nanometer transistor on analog performance

Abstract

Scaling down of transistor dimension is generally being well accepted and adapted by digital designers as they could introduce more design features at almost no increase in silicon area. However, for analog designers, using smaller transistors in their design would cost them extra design efforts as they have less design headroom in hand –amongst others are low supply voltage, signal to noise ratios and transconductance. These issues become more obvious as designers are now using transistor size in nanometer region. This calls for better understanding on how smaller transistor affect circuit performance. This research addresses the above issues, using predictive transistor model, process technologies of 130 nm, 90 nm, 65 nm, 45 nm, and 32 nm as case studies. Analyses have been be carried out to understand which of the analog performances such as gain, power dissipation, output voltage swing, and cut-off frequency would be severely affected as the process shrinks to nanometer region. The circuits designed for the research have also been subjected to variations in process corner namely typical, slow, and fast. The outcome of the research points out several disturbing impacts of nanometer size transistors. First of all, its impact on analog performance of cascode amplifier is truly a great concern. Low voltage supply in nanometer transistors presents a design challenge to cascode amplifier in circuit design. Almost all its major performances are severely affected. For telescopic amplifier circuit, the analog performances such as gain and cut-off frequency are also greatly affected due to linearity issues of the design when one moves toward smaller transistor sizes. However, results on differential circuits have some positive news as it helps soften the impact on voltage gain and voltage swing. It is also worth to mention that based on rough estimation, designers would take longer time to complete the design task, thus slowing down the time of manufactured devices to be marketed.