Operational Transconductance Amplifier Macromodel Optimization For Active Piezoelectric Filter Design

This work addresses the problem of optimal operational transconductance amplifier (OTA) macromodel creation in terms of its application in active FBAR filters. Existing macromodels of active elements are reviewed from their structure and application point of view. A nonlinear macromodel of OTA was developed on the basis of single-pole three-stage macromodel, which takes into account the necessary effects of real devices: the finite input and output impedances, the frequency dependence of transconductance coefficient and its nonlinearity behavior, noise characteristics. The features of presented solution include versatility of application in most of nowadays CAD systems, the ability to estimate with sufficient accuracy the frequency response of the filter and its performance, dynamic range, harmonic and noise analysis. Simple structure allows the speed-up of calculation and direct digital optimization techniques can be adopted to optimize the characteristics of the filter. The verification of macromodel was demonstrated on the example of FBAR connected to gyrator circuit, which showed high precision imitation of transistor-level circuit. The analysis of transient response and harmonic balance proved the acceptance of power series approximation of operation range. The use of two diodes outside this range allowed for modeling in wide input voltages range. The developed macromodel can be successfully used for the synthesis of active FBAR filters