Research And Design Of CSTA-based Current-mode Filter And Oscillator

In recent years,with the rapid development of microelectronic technology,the demand for analog integrated circuit in the integrated degree,power,frequency and other aspects of performances has been on a great upsurge.In the analog signal processing circuits,filter and oscillator circuits as a basic link have been actively researched in industrial and academic fields.Current mode circuits have been put in a very important position by the majority of designers of integrated circuits due to its the characteristics of low power supply voltage,fast switching speed,high linearity,wide dynamic range,etc.Because current differencing transconductance amplifier(CDTA)is a synthesis of the advantages of the other current mode active building blocks,it showed a greater advantage in analog signal processing circuits.Therefore,CDTA and its application circuits is a front subject in microelectronics,integrated circuits and system both in domestic and overseas.This paper mainly studies on the CDTA and its applications in current mode filter and oscillator circuits.First,it introduces the concept,character and development of the current mode circuit.Afterwards,the CDTA and its research status in current mode filters and oscillators are introduced.Then,it introduced the theory,design method and the development situation of filter and oscillator circuits.Finally,based on the above background,by reading the literature and theoretical analysis,we propose a novel current mode biquad filter circuit and two current mode multiphase sinusoidal oscillator(MSO)circuits.The main innovative work and results of this study are as follows:(1)A new CDTA-based current mode biquad filter circuit is presented.The proposed filter enjoys the advantages of simple structure,suitable monolithic integration,electronically adjustable,low sensitivities and multiple functions,etc.PSPICE with TSMC 0.18 um technology has used to simulate the designed filter,and simulation results verified its performance.(2)Two kinds of new current mode multiphase sinusoidal oscillator circuits have been proposed: Current controlled current differencing unit(CCDU)-based current mode MSO circuit;Current differencing cascaded transconductance amplifier(CDCTA)-based current mode MSO circuit.Among,the CCDU-based current mode MSO has simple topology with least transistors.The circuit only consists of CCDUs and the grounded passive elements,which is easy for integrated circuit(IC)fabrication.The presented MSO provides 2n(n?2)phase signals that are equally spaced in phase and equal amplitude.The theoretical results were confirmed by PSPICE simulation.The CDCTA-based current mode MSO,which uses only one active device and a small amount of grounded passive elements,have highly integrated degree.Its oscillation condition and oscillation frequency can be controlled electronically and independently through adjusting the bias currents of the CDCTA.Moreover,the circuit has some advantages in power consumption,bandwidth,input and output resistances,etc.CADENCE simulation and experimental results are included to verify all the theory.At last,the paper summarizes the proposed current mode filter and oscillator circuits,and has put forward the direction of the future.