Selection of the common-mode feedback network connection of fully differential Gm-C filters

Mahattanakul, J.; Khumsat, P.; Surakampontorn, W.

doi:10.1049/iet-cds:20080225

Selection of the common-mode feedback network connection of fully differential Gm-C filters

Author(s)

Mahattanakul, J.

Khumsat, P.

Surakampontorn, W.

Date Issued

February 10, 2009

Type

Article

DOI

10.1049/iet-cds:20080225

Abstract

It is well known that fully differential (FD) structures have many advantages over their single-ended counterparts. However, the main disadvantage of FD circuit is the potential instability caused by the inherent common-mode (CM) positive feedback loop. To solve such an instability problem, extra common-mode feedback (CMFB) and/or common-mode feedforward (CMFF) circuitries are often incorporated to stabilise the circuits. We present a systematic method for checking the stability condition and identifying the most suitable CMFB network connection for a particular FD Gm-C filter. It has been demonstrated that the CMFB network connection that provides highest CM rejection is not necessarily the conventional arrangement commonly used in FD Gm-C design. © The Institution of Engineering and Technology 2009.

Citation

Iet Circuits Devices and Systems, 3(1), 49-56, 2009