Continuous-time filters (CTF) with automatictuning loops are nonlinear feedback systems with potential instability. Therefore, the appropriate linear dynamic modeling of the tunable filter should be obtained to assure stability in case an improved design of the loop controllers is to be carried out. With this aim, starting from a general and systematic analysis in order to obtain an equivalent small-signal linearised incremental model, from which transfer functions between output variables and control voltages are derived, the subsequent design of compensated loops with enhanced stability and dynamic performance is proposed. In particular, this modeling allows proposing both a non-adaptive and adaptive controllers with improved stability, together with their implementation. As a demonstrative example of application, the modeling of a particular band-pass CMOS CTF is presented in this paper. Experimental results are shown for a CMOS 0.8-(mu)m technology.
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