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In the last few decades, the analogue designers more thought about processing signal by current mode signal. As the current mode circuit compares with the voltage mode circuit, the former proves to be two conceptual advantages: higher frequency capabilities and larger dynamic range. And the architecture of current mode circuit form, it is more convenient and direct to copy or operate the signal than the voltage mode. Such as the switch current filter in the recently developing.
In this thesis, a new CMOS current operational amplifier (COA) with fully differential input and differential output is proposed and analyzed. The amplifier is implemented from a differential current mirror input transimpedance stage followed by a differential output transconductance gain stage. A differential mode design technique is proposed and used in the feedback circuit. The simulation results of the new COA are based upon the 0.5um CMOS process and ±1.5V supply voltage. The new COA exhibits an open-loop differential gain of 51.71dB with the gain-bandwidth product 314MHz and a settling time of 14ns.
To design VLSI circuit in the recent, the mix mode circuit design is the future trend in order to cooperate with the digital process. So the low voltage, and low power analogue circuit design is indispensable. Specially in the mobile personal communication system. So in this paper, we first analysis the basis current cell circuits, e.g. low voltage current mirror. And we will discuss the property of the circuit, as follows describe:
(a) bandwidth improvement
(b) parasitic capacitor effect improvement
(c) unit step function time response
(d) temperature stability discussion
(e) bias circuit and dynamic range discussion
In the last, the applications of the COA in processing current signals are proven to be the counterpart of the traditional voltage mode operational amplifier (VOA). The current integrator and the current Biquad filter show their duality with voltage integrator and Biquad. In the domain of filter design, COA is proven to be applicable to MOS-C current filter as well as SC voltage filter. Thus this COA can be used to process the signals on chip.
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