Noise and Sensitivity Improvement using SC Filters

The discrete time switched capacitor (SC) based filters have number of advantages over the classical continuous time active RC based filters, the one most important being reduced circuit silicon area, allowing SC filters to be integrated to a single monolithic integrated circuit (IC). In this paper we have designed fifth order Chebyshev low pass SC filter, with a cut-off frequency f_x=3.4 kHz, and pass-band ripple a_ma x =-0.5 dB, and we have compared its time and frequency performance with a performance of the active RC based filter. The both SC and active RC filters are realized as a cascade of two second order sections and one first order section. All filter analysis has been performed using MATLAB and SPICE program packages where SC based filter has shown significant noise and sensitivity improvement, when compared with active RC based filter.
Vremensko diskretni filtri s preklapanim kapacitetima imaju niz prednosti nad klasičnim vremensko kontinuiranim aktivnim RC filtrima. Jedna od važnijih prednosti jest smanjena površina silicija, omogućavajući integraciju filtra u integriranoj thenologiji (IC). U ovom radu dizajniran je Chebyshev nisko propusni filtar s preklapanim kapacitetima s graničnom frekvencijom f_c = 3.4 kHz i valovitosti alpha_max = -0.5 dB, te su mu vremenska i frekvencijska svojstva uspoređena sa svojstvima aktivnog RC filtra. Oba filtra realizirana su kao kaskada dviju sekcija drugog reda te jedne sekcije prvog reda. Analiza oba filtra izvršena je u MATLAB i SPICE programskim paketima, te je kod SC filtra pokazano znatno smanjenje šuma i osjetljivosti u usporedbi s aktivnim RC filtrom.