Generation of continuous-time two integrator loop OTA filter structures

Generation of two integrator loop filter structures using operational transconductance amplifiers (OTAs) and capacitors (TAC) is presented. A direct block diagram approach is used to generate the TAC filter structures. The basic filter building blocks consist of a lossless integrator, lossy integrators and the three types of summers. They are implemented using OTAs as the active components. The resulting TAC second-order filter structures, some previously reported and others new structures, are generated in an orderly way. It is shown that the selection of the best structure depends on the particular application or design specifications. The generated TAC biquadratic structures are only very suitable for monolithic filters since typically only OTAs and two capacitors are needed. A TAC filter structure homologous to the conventional KHN op amp filter structure is presented. Programmability of ω_p, Q_p and voltage gain is considered