Closed-loop filters are widely used in several mixed-signal systems. They are often preferred to the open-loop gm-C counterpart for the intrinsic in-band linearity provided by the large in-band loop-gain. Unfortunately, all feedback analog filters suffer from poor linearity when the input tones frequency is in close proximity to the closed-loop poles frequency, where loop-gain reduces. This concept is not included in the Figure-of-Merit (F.o.M.) widely used in the past to compare different filters designs, in different technology processes. In this scenario, the aim of this paper is to provide a more complete F.o.M. that includes the linearity performance frequency dependence. In order to validate these considerations, this work presents and models the most relevant harmonic distortion metrics (IIP3 and IM3) as a function of the loop-gain frequency behavior. The reference schematic is a classical CMOS 0.18μm 1st-order filter based on a fully-differential Operational Amplifier (Opamp). Finally the whole analog filters State-of-the-Art is compared using the classical F.o.M. and the hereby proposed F.o.M.
Fary, F., Vallicelli, E., De Matteis, M., Baschirotto, A. (2018). About figure-of-merit for continuous-time analog filters. In 2018 International Conference on IC Design & Technology (ICICDT 2018) Proceedings of a meeting held 4-6 June 2018, Otranto, Italy (pp.57-60). Institute of Electrical and Electronics Engineers Inc. [10.1109/ICICDT.2018.8399755].
About figure-of-merit for continuous-time analog filters
Fary, F;Vallicelli, EA;De Matteis, M;Baschirotto, A
2018
Abstract
Closed-loop filters are widely used in several mixed-signal systems. They are often preferred to the open-loop gm-C counterpart for the intrinsic in-band linearity provided by the large in-band loop-gain. Unfortunately, all feedback analog filters suffer from poor linearity when the input tones frequency is in close proximity to the closed-loop poles frequency, where loop-gain reduces. This concept is not included in the Figure-of-Merit (F.o.M.) widely used in the past to compare different filters designs, in different technology processes. In this scenario, the aim of this paper is to provide a more complete F.o.M. that includes the linearity performance frequency dependence. In order to validate these considerations, this work presents and models the most relevant harmonic distortion metrics (IIP3 and IM3) as a function of the loop-gain frequency behavior. The reference schematic is a classical CMOS 0.18μm 1st-order filter based on a fully-differential Operational Amplifier (Opamp). Finally the whole analog filters State-of-the-Art is compared using the classical F.o.M. and the hereby proposed F.o.M.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
