A general framework for evaluating nonlinearity, noise and dynamic range in continuous‐time OTA‐C filters for computer‐aided design and optimization

Abstract

SUMMARYEfficient procedures for evaluating nonlinear distortion and noise valid for any OTA-C filter of arbitrary order are developed based on matrix description of a general OTA-C filter model. Since those procedures use OTA macromodels, they allow us to obtain the results significantly faster than transistor-level simulation. On the other hand, the general OTA-C filter model allows us to apply matrix transforms that manipulate (rescale) filter element values and/or change topology without changing its transfer function. Due to this, the proposed procedures can be used in direct optimization of OTA-C filters with respect to important characteristics such as noise performance, THD, IM3, DR or SNR. As an example, a simple optimization procedure using equivalence transformations is discussed. An application example of the proposed approach to optimal block sequencing and gain distribution of 8th order cascade Butterworth filter is given. Accuracy of the theoretical tools has been verified by comparing to transistor-level simulation results and to experimental results.

High‐tuning‐range CMOS band‐pass IF filter based on a low‐Q cascaded biquad optimization technique

“…Because of its complexity, the only way to find truly optimal solution of the general problem is exhaustive search through all possible cascade sequencing and performing parameter optimization for each of them . To facilitate and simplify this task, macromodels (based on the matrix description of the general G m ‐C filter class ) for the evaluation of nonlinear distortion, noise, and dynamic range were proposed in . These macromodels are suitable to be implemented in a fast computer‐aided design tool to avoid time‐consuming transistor‐level simulations, so that a direct numerical optimization becomes practically feasible.…”

Computational assessment of methods to analytically obtain the transient response of LTI circuits

“…For instance, the analysis of continuous-time analog filters and equalizers, based on transconductance amplifiers and capacitors (OTA-C filters), is dealt with in [8][9][10]. This type of filters constitute suitable solutions for various voltage-mode and current-mode signal-processing tasks over wide frequency ranges.…”

Current‐mode biquadratic filter using DO‐CCCDBAs

“…A Current-Controlled-Conveyor II (CCCII) and Operational Transconductance Amplifier (OTA) whose x-port resistance and transconductance are electronically controllable, have been recently used to realize electronically controllable current-mode biquad filters, for instance, see [25][26][27][28][29][30][31] and the references cited therein. In this paper, we have focused on how DO-CCCDBAs can be used to realize electronically controlled biquad filters along with a number of advantages.…”