Performance optimization methods for switched-capacitor biquadratic filters

A class of computer-aided optimization methods based on Differential Evolution (DE), Particle Swarm Optimization (PSO) and Nelder Mead algorithms applied to a switched-capacitor (SC) filter circuit design are investigated. Comparisons of these algorithms applied to a 4th order biquadratic two-channel filter bank CMOS design on 0.35 µm technology are made. The frequency responses of the biquadratic filters must match ideal responses in a finite number of iterations with a limited number of “particles”. The original and derived methods are evaluated on the base of their convergence progress and their reliability over different starting populations. An optimal design approach based on combining algorithms is derived as a more suitable and more reliable method for SC circuit optimization.

Programmable Universal Filters Using Current Conveyor Transconductance Amplifiers

This paper presents new programmable universal biquadratic filters using current conveyor transconductance amplifiers (CCTAs) by which both voltage- and current-mode filters can be obtained. The proposed filters use second-generation current conveyor (CCII) which is the first stage of CCTA to operate as current conveyor analog switch (CCAS) and this CCAS will be used to program the filtering functions such as low-pass, high-pass, band-pass, band-stop and all-pass filters. Unlike previous universal filters, the filtering functions of the proposed filters can be programmed using the bias currents of CCTAs without changing any input and output connections. The natural frequency and quality factor of all filtering functions can be controlled electronically and orthogonally using the bias currents of transconductance amplifiers. Also gain response of all transfer functions can be adjusted. The active and passive sensitivities of the filters are low. The proposed programmable filters have been simulated using 0.18[Formula: see text][Formula: see text]m CMOS process from TSMC. PSPICE simulation results are included to confirm workability of the proposed circuits.

Design of OTA-C Gaussian Function Generator

A novel method for analogue VLSI implementation of programmable Gaussian function generator is proposed in this paper, in which the Gaussian function is approximated by the OTA-C filter whose frequency response is Gaussian-shaped. OTA-C circuit is very suitable for this application since the programmability can be controlled by the transconductance of OTA precisely and easily. Based on the probability argument, the OTA-C biquadratic filters and OTA-C integrator which have the cascade connection are used as the building block. To elaborate the construction procedure, a seventh-order OTA-C Gaussian function generator is selected as an example. The simulation results verify the feasibility of the presented approach.