Design of versatile current mode active elements for mixed mode universal filters and oscillators

Abstract

The current mode (CM) analog circuits can operate at low supply voltage with high performance in terms of signal bandwidth, accuracy, dynamic range etc. These attributes make them ideal for designing battery operated electronic systems, implantable biomedical devices and the internet of things (IoT) architecture. The low voltage low power (LVLP) operation is the mandatory prerequisite for modern electronic systems. In the present digital age analog systems still hold prominent place due the fact that all naturally occurring signals are analog. Processing signals in analog domain is much faster and consumes less power as there is no requirement to convert the signal from analog to digital domain and again back to analog domain after processing as is the case with digital signal processing. The present-day requirement of high speed and smaller size can only be achieved by hybrid analog and digital signal processing systems. Where, the initial processing is accomplished by analog part and the complex signal processing task is performed by the digital processor. The two most important analog signal processing modules are the analog filters and oscillators. The filters are the main components in data acquisition systems, communications systems, navigation systems etc. They perform task like frequency selection, noise filtering, phase correction, signal equalization etc. The oscillators perform signal generation, comparison and synchronization tasks. The main aim of this thesis is to define and design new LVLP analog current mode active elements (CMAEs) for carrying out analog signal processing tasks. The work in this thesis can be divided in to two parts. The first part introduces architecture of three novel CMAEs. The voltage differencing Extra X current conveyor (VD-EXCCII), the voltage differencing dual X current conveyor (VD-DXCC), the voltage differencing differential difference current conveyor (VD-DDCC). In the second part, the designed CMAEs are employed in the design of nine novel structures of mixed mode universal filters that can work in current mode (CM), voltage mode (VM), trans-admittance (TAM) mode and trans-impedance (TIM) mode. In addition, three novel topologies of mixed mode oscillators are also designed including, a third order oscillator. All the designed signal processing units require minimum number of both active elements and passive components. The workability of the designed CMAEs, mixed mode filters and oscillators is established through mathematical analysis and further verified by post layout simulation analysis. The cadence analog design environment tool along with the Silterra Malaysia 0.18μm product design kit (PDK) is used for the analysis. The designed CMAEs work at supply voltage in the range of 1V to 1.25V. The power dissipation of the proposed CMAEs is found to be in the range of 900μW to 3mW. The power consumption of the designed filters and oscillators are found to be in the range of 1mW to 5mW.