PGAs and Filters

Abstract

Amplifiers and filters are commonplace devices in the analog front-end (AFE) of communication transmitters-receivers (transceivers, in short). In a general sense, these devices provide the necessary adaptation, in terms of power adjustment and signal isolation, between the transmission media (e.g., atmosphere, free space, cable, twisted-pair, optic fiber) and the digital signal processor (DSP) which performs most of the algorithmic tasks needed to guarantee a reliable transmission/reception of the information [1]. In some cases as, for instance, in wireless transceivers, amplification and filtering may take place at multiple steps along the AFE; often using different technologies (CMOS, silicon bipolar, GaAs) or external passive components (e.g., surface-acoustic wave filters) depending on the frequency range at which operations are realized [2]. In this chapter, following the main stream of the book, we focus on the realization of those amplifiers and filters which are used to drive signals to/from the AFE data converters†2 at the interface with the DSP block, paying special attention on their implementation in inexpensive CMOS technologies. Such amplifiers and filters are symbolically shown in Fig. 14.1, where preceding/following circuits for reception/transmission have been globally called Rx/Tx medium interface, respectively.