The present invention provides tetrahydropyrvinium, derivatives thereof, benzoxazole compounds, and derivatives thereof. Each of the SMT MRAM cells of the column is connected to a true data bit line and each of the SMT MRAM cells of the associated pair of columns is connected to a shared complement data bit line. 5, and Z is selected from a group consisting of rare earth metals other than europium. Charge compensation devices are used to enhance the performance of bottom-plate sampling systems as well as bootstrapped TH circuits. A single drive controls both the first starter-generator and the second starter-generator such that their electrical current and power inputs are minimized and balanced. From these last measurements a complex calibration ratio for all of the elements being calibrated with respect to a single element is determined.