Luis M. Camarinha-Matos (Ed.): DoCEIS 2011, IFIP AICT 349, pp. 565–572, 2011. © IFIP International Federation for Information Processing 2011 CMOS Fully Differential Feedforward-Regulated Folded Cascode Amplifier Edinei Santin, Michael Figueiredo, João Goes, and Luís B. Oliveira Departamento de Engenharia Electrotécnica / CTS – UNINOVA Faculdade de Ciências e Tecnologia (FCT) / Universidade Nova de Lisboa (UNL) 2829-517 Caparica – Portugal {e.santin,l.oliveira}@fct.unl.pt, {mf,jg}@uninova.pt Abstract. A fully differential self-biased inverter-based folded cascode amplifier which uses the feedforward-regulated cascode principle is presented. A detailed small-signal analysis covering both the differential-mode and the common-mode paths of the amplifier is provided. Based on these theoretical results a design is given and transistor level simulations validate the theoretical study and also demonstrate the efficiency and usefulness of the proposed amplifier. Keywords: fully differential amplifiers, feedforward-regulated cascode technique, self-biasing, inverter-based, CMOS analog integrated circuits. 1 Introduction Amplifiers are essential building blocks used frequently to build feedback networks able to perform a variety of accurate functions, e.g. multiplication, addition, integration, inversion, etc. The accuracy of these operations is directly dependent on the amplifier’s gain-bandwidth product (GBW) performance [1]. Dictated by the down scaling of the digital circuits, the CMOS technology evolved posing several obstacles to the analog circuits design in general and in particular to the amplifiers design. Some of these obstacles are low intrinsic gain (g m /g ds ) of transistors, reduced supply voltages, high variability of devices, etc., which inevitably deteriorate the performance of the well-known amplifier topologies. To cope with this problem some existing amplifier topologies have been enhanced and novel topologies have been proposed, some recent examples are [2]-[4]. In this paper we propose a fully differential self-biased inverter-based folded cascode amplifier which uses the feedforward-regulated cascode principle firstly presented in [4]. First, the small-signal behavior of the topology is analyzed in detail. After, a design is outlined and transistor level simulations are presented to demonstrate the efficiency of the proposed new topology. Finally, the main conclusions are drawn. 2 Contribution to Sustainability A new self-biased inverter-based transconductance amplifier topology using feedforwad-regulated cascode devices is presented. The combination of these features