Systematic design of CNTFET based OTA and Op amp using gm/ID technique

Abstract

This paper presents for the first time all the steps required in optimal design of carbon nano tube field effect transistor (CNTFET) based single stage operational transconductance amplifier and two stage operational amplifier using transconductance to drain current ratio ($$g_{m}/I_{D}$$) technique for low voltage and low power applications. As square law model failed to produce exact behavior in short channel devices as well as moderate and weak inversion behavior of the transistor. Therefore, $$g_{m} / I_{D}$$ methodology is used to design analog circuits in short channel devices to overcome the shortcomings of square law models. Also, the design using $$g_{m} / I_{D}$$ methodology does not consider the inversion region of the transistor like square law equations. The $$g_{m} / I_{D}$$ methodology is a well-established technique for CMOS analog IC design but CMOS has continuous width while CNTFET width is discrete and depends on different parameters like number of tubes, pitch and diameter of the carbon nanotube. Therefore, there is a need of a design methodology to design analog circuits using CNTFETs. Circuit performance has been investigated extensively using HSPICE simulation.