Circuit Model Approach Research Articles

Modeling of magnetic field sensitivity of bipolar magnetotransistors using HSPICE

In this paper, we present simulation results of magnetic sensitivity for bipolar magnetotransistors using an equivalent circuit modeling approach. The magnetotransistors is suitably partitioned into inactive- and active-magnetic device regions where the latter is modeled using an appropriate circuit topology, based on magnetic field dependent resistors and voltage controlled current sources that account for the interaction of the magnetic field on the injected currents. The resulting equivalent circuit is generated and implemented into HSPICE and simulation results, and subsequent optimization, of magnetic sensitivity are obtained for various geometrical and technological parameters. The circuit approach presented here facilitates computer aided design (and optimization) of both sensor, the co-integrated circuitry, and their interactions, since it can all be done in the same environment. >

The shortcomings of pure circuit models of transducers

Circuit models of transducers have been used for decades and have proven to be useful tools for prediction of transducer behavior. In this approach, the transduction mechanism is typically modeled using ideal two-port transformers or gyrators that neither dissipate nor store energy. Energy loss and storage are taken into account using one-port elements connected to the transducing gyrator or transformer. An alternative approach to transducer modeling recognizes that the transduction mechanism itself generally is associated with energy storage or dissipation. In this formulation, the transduction mechanism is typically modeled using a two-port energic element (such as a two-port capacitance). A comparison of the two formulations for piezoelectric transducers shows that there are two fundamental shortcomings introduced in the circuit model approach that are not present in the energic multiport element approach: The transformer modulus must be made a function of the strain of the piezoelectric material, and it is not possible to discuss the piezoelectric material response without imposing a load on the transducer. It is concluded from this analysis that circuit models fail to represent accurately energy exchange in transducers.