IMPLEMENTATION OF ANALOG CIRCUITS USING CDTA AND CDDITA

Abstract

A new CMOS realization of the current differencing differential input transconductance amplifier (CD-DITA) and CD-DITA based voltage mode MISO-type universal biquad filter are proposed. CD-DITA is an extension of CDTA having extra voltage input than CDTA increasing its usability of differential inputs. For a suitable CMOS based implementation of CD-DITA, several CDTA realizations are studied and the suitable one is modified to implement the proposed CD-DITA block. A FVF based DO-CDTA is characterized and its applications in analog signal processing circuits such as basic amplifiers, signal generators such as Schmitt Trigger and KHN filter are also studied. The proposed CD-DITA based voltage mode MISOtype universal biquad filter is realized with two resistors and two capacitors with independent electronic control of natural frequency and quality factor. The proposed filter can implement all five second order low pass, high pass, band pass, band stop, and all pass filter responses without altering the circuit topology. The proposed filter also offers low active and passive sensitivities. In addition, the effects of parasitics and errors on the proposed filter are also investigated. The characteristics CDTA and its applications are verified by PSPICE simulations using TSMC 0.25μm CMOS technology. The characteristics of CD-DITA and validity of proposed universal biquad filter is verified by SPICE simulation using TSMC 180nm technology.