Search

In this article, all possible wideband fully differential second-order voltage-mode active all-pass filters (APFs) based on a common-source differential amplifier are systematically derived using two-port network modeling techniques and symbolic math CAD tools. The proposed APF structure is based on the generic two-transistor differential-pair and all possible combinations of the surrounding impedances. In particular, 26 transfer functions and a total of 180 APF circuits, all of which can have a pole quality factor ($Q$) value greater than unity, are found to be possible. Hence, the proposed topology can be used to produce APFs with dispersive delay as well as flat delay for true time delay elements. The operation of some APFs is verified with simulations and a selected circuit with tunable peak delay is designed and fabricated in a 65-nm CMOS process. The implemented filter achieved a maximum peak delay of 88.4 ps at 31 GHz, a constant delay of 11.5 ps over the frequency band 5–20 GHz, and a delay $Q$ -factor ($Q_{D}$) value of 3.74, while consuming 1.74 mW from a 1-V supply voltage. The fabricated circuit occupies an area of $0.11\times 0.348$ mm2 and experimentally demonstrates an APF with the highest $Q$ value of any published second-order APF known to the authors. [ABSTRACT FROM AUTHOR]

In this paper, the generation of differential-input differential-output second-order active filters based on a common-source differential amplifier is systematically conducted using two-port network modeling techniques which enable exploiting the power of symbolic math CAD tools. Starting from a generic two-transistor differential-pair structure, and the maximum possible number of surrounding impedances, all possible filters are derived and classified. In particular, 35 transfer functions and a total of 876 filters are found to be possible. Due to employing a $2\times 2$ transmission matrix representation of each transistor, flexibility in examining parasitic effects on the derived transfer functions is achieved and can be easily automated within the design framework. Selected filters are constructed and experimentally verified using discrete transistors. The operation of some filters is also verified with simulations using a 65-nm CMOS process. [ABSTRACT FROM AUTHOR]

A circuit for the generation of amplitude-matched balanced signals from a single-ended or differential source is presented. The circuit is accurate, wideband, and has a good phase performance without matched amplifier poles. It is based on a structure utilizing operational conveyors that have a differential input, easily adjusted gain, and voltage or current outputs. [ABSTRACT FROM AUTHOR]