Theoretical Model of Ungrounded Inductance Realized With Two Gyrators

The traditional approach to simulate ungrounded inductors in active gyrator filters uses two gyrators with all equal transconductances. However, this paper shows that the differences between gyrator transconductances can be employed to obtain certain advantages. The filter can be designed with extra gain and with different terminating resistors, but without need of any additional buffer amplifiers. These advantages are achieved by using an appropriate theoretical model of the gyrator simulated floating inductance in the filter design process. The model separates the simulated inductance from the amplification, thus suggesting more flexible filter design. Further the model is extended to reflect also some OTA imperfections-their input and output impedances and their noise generation. In addition, the discussed model gives a unified approach for theoretical analysis of gyrator LC filters with floating inductors.