High-gain current amplifiers for low-power MOSFET-C filters

Current amplifiers have been proposed as alternatives for low-power MOSFET-C or active-RC filters. High gain of the proposed current amplifiers relies on internal high impedance nodes. Such high impedance is realised using positive feedback cross-coupling configuration to cancel its negative feedback counterpart. Two different output stages, namely class-A and class-AB are also introduced. Bias circuits suitable for the proposed amplifiers are also introduced where they further help minimise power consumption and silicon area in a high-order filter design. The proposed circuits employed in a simple second-order filter were compared with a conventional folded-cascode OTA amplifier under 1-V supply. Simulation results with 0.18mum CMOS process indicate correct functionalities and superior linearity performance offered by the proposed amplifiers