Quantum mechanical modeling and implementation of single electron transistor circuit

Abstract

Different models of nano-electronic quantum device Single Electron Transistor (SET) are studied in this work, a modified macro model is proposed and at the end its application in a communication circuit is presented. In the modified macro model it is shown that an inherent problem in the earlier model like unwanted DC offset has been successfully eliminated. I-V characteristics curve of the SET has been studied very closely with the modified macro model. It is shown that how coulomb oscillation of SET can be used to form variable transconductance region of operations. The variable transconductance region of SET consists of a positive and a negative part and a new phenomenon named ‘negative transconductance’ is observed which is very unique to SET. It is also described how to bias a circuit to achieve that condition with the operating principle described, a phase modulator circuit is proposed in this work which utilizes negative transconductance. The circuit exploits the unique characteristics of SET of having bi-polar transconductance for the proper operating point. The biasing of the circuit is the one of the most critical parts since the region of operation is very narrow. Different biasing conditions are also discussed for the SET bases phase modulator circuit. Since almost every form of communication signal handing systems always convert the original signal to a modulated signal for further processing and increase gain of the transmitted signal, Phase modulator is one of the most common of all elementary communication circuit configurations. The SET based digital signal phase modulator circuit proposed in this work is the most simplified for such circuits used so far. It is seen from the simulation data that SET based digital signal phase modulator circuit performs very efficiently to convert digital pulse to modulated signal.