Research And Design Of CMOS Current Differencing Buffer Amplifier And Current Mode Filter

As the development in VLSI circuits, there is a growing interest in current modecircuits due to their better linearity, wider bandwidth, simpler architectures and lowersupply voltage characteristics than their voltage-mode counterparts. As a basicbuilding block of the current mode circuit, current differential buffer amplifier canprovide wider bandwidth and better accuracy compared with voltage mode operationalamplifiers. However, current differencing buffer amplifier being implemented withthe existing techniques suffer from the intrinsic resistance in the current inputterminal, which leads to a relatively significant voltage tracking error in the voltagetransfer, for the moment, current controlled current differencing buffer amplifier isthe best solution to the problem.A new low voltage low power high performance current differencing bufferamplifier (CDBA) which based on all NMOS mirrors, designed in a UMC0.5μmCMOS technology, is presented in this paper. The low voltage low power CDBA onlyconsists of a current subtraction circuit and a voltage follower. The first stage currentsubtraction circuit utilizes a low-voltage current mirror which is followed by animproved Wilson mirror to attain a low supply voltage and wide bandwidthsimultaneously. A basic mirror and a Wilson mirror constitute the voltage followerachieves good voltage gain accuracies and low impedance at voltage output terminal.The implemented low voltage and low power CDBA presents great voltage andcurrent gain accuracies of1.02,0.99, respectively. An excellent input impedance of12was obtained in the required band with a power dissipation of0.48mW under asupply voltage of±0.8V. The-3dB bandwidth is about726MHz.Finally, the new low voltage low power high performance current differencingbuffer amplifier (CDBA) is used for an application in Current-mode filter. A newcurrent mode high order filter and a new second-order filter circuit which have beenrealized, are based on a new low voltage low power high performance currentdifferencing buffer amplifier (CDBA). The current mode high order filter andsecond-order filter circuit is simulated by Pspice with0.5μm technology in order toindicate that this filter is feasible. And the simulation results show that the currentmode filter circuit offers several advantageously features such as high slew rate, free from parasitic capacitance, wide bandwidth, low power, and simple implementation.