Current Controlled Fully Balanced Current Conveyor And Its Filter Research

As the development in VLSI circuits, there is a growing interest in current mode circuits due to their better linearity, wider bandwidth, simpler architectures and lower supply voltage capabilities than their voltage-mode counterparts. As a basic building block of the current mode circuit, current conveyors can provide wider bandwidth and better accuracy compared with voltage mode operational amplifiers. However, current conveyors being implemented with the existing techniques suffer from the intrinsic resistance in the current input terminal, which leads to a relatively significant voltage tracking error in the voltage transfer, for the moment, current controlled current conveyors are the best solution to the problem.In the VLSI circuit, the noise, actually the common mode signals, aroused by the digital part would influence the analog part, while current conveyors with fully balanced structure can effectively suppress these noise, moreover, differential filters implemented by the fully balanced current conveyors can filter out the noise.This dissertation mainly focuses on the study of the realization of a current controlled current conveyor with fully balanced structure and its application in current mode filters, amplifiers and universal current conveyors. Firstly, the research situation of the development and filter application of current conveyor is summarized. The port characteristics, circuit principles and typical circuit realizations of current conveyor and its filter applications are introduced in detail. Then, the creative studies on the current controlled fully balanced current conveyor and its applications on filters, amplifiers and universal current conveyors are investigated. The main innovative work of this dissertation is as follows.(1) This dissertation proposed a current controlled fully balanced current conveyor (CFBCCII), the circuit introduces a current controlled resistance to the fully balanced current conveyor, the resulting circuit not only has the advantage of fully balanced structure, but also can be controlled by the bias current. All the terminals of CFBCCII are differential, and the circuit can restrain common mode signals effectively in virtue of the introduction of the common mode feedback block. The voltage input cell is implemented from a translinear loop composed of CMOS compound transistors, which can eliminate the voltage transfer errors in the conventional current conveyors. Moreover, the intrinsic resistance of CFBCCII lowers the number of the passive elements when implementing various application circuits, and the parameters of the application circuits can be tuned by the bias current.(2) The dissertation proposed3CFBCCII based second-order current-mode filters, including a multi-input single-output filter based on a single CFBCCII and two multi-input multi-output filters based on multi-CFBCCII. The multi-input single-output filter based on a single CFBCCII is single ended, the circuit employs one CFBCCII, two grounded passive elements. In virtue of CFBCCII, the filter does not need any resistors. Numerous filtering functions can be obtained depending on the status of the input current. The natural frequency and the quality factor can be tuned independently.The rest two filters are both differential, the first one employs2CFBCCIIs and4pairs of grounded passive elements, the second one uses3CFBCCIIs and2pairs of grounded passive elements, both filters can realize low-pass, ban-pass and all-pass filtering functions, the natural frequency and the quality factor are independently tuned.The layout design is also carried out for the CFBCCII circuit, CFBCCII based single ended multi-input single-output filter and the differential multi-input multi-output filter based on3CFBCCIIs, eventually, the above three circuits are taped out successfully with Chartered0.35μm process.(3) A current mode high order elliptic filter was proposed based on CFBCCII with leapfrog synthesis, this filter is differential, which can suppress common mode signals effectively, and the cutoff frequency can be controlled by the bias current of CFBCCIIs. The Leapfrog synthesis is simple and intuitive, moreover, the filter inherit the low sensitivities of passive RLC ladder filters.(4) This dissertation proposed a universal current conveyor based on CFBCCII, the proposed circuit can realize many kinds of current conveyors conveniently. Two kinds of current mode and voltage mode amplifiers based on CFBCCIIs are also proposed as the application of CFBCCII, the gains of the amplifiers can be adjusted by the bias current of CFBCCII.