Active filters for intermediate frequencies using low-gain transducers

Second-order active networks are investigated, using all four possible types of dependent sources with relatively low gains. All proposed structures use two imperfect integrators and one low-gain feedback amplifier. It is shown that the sensitivities of these networks to changes of all elements are low provided certain conditions are fulfilled. The influence of the finite gain-bandwidth product of the dependent sources is studied and it is shown that the sensitivities remain low as Q increases. It is also shown that current-controlled sources make better active filters than voltage-controlled sources (i.e., operational amplifiers). The networks are suitable for use in intermediate frequency regions.