US Patent 9697882 Analog ferroelectric memory with improved temperature range

A ferroelectric memory and a method for operating a ferroelectric memory are disclosed. The ferroelectric memory includes a ferroelectric memory cell having a ferroelectric capacitor characterized by a maximum remanent charge, Qmax. A write circuit receives a data value having more than two states for storage in the ferroelectric capacitor. The write circuit measures Qmax for the ferroelectric capacitor, determines a charge that is a fraction of the measured Qmax to be stored in the ferroelectric capacitor, the fraction being determined by the data value. The write circuit causes a charge equal to the fraction times Qmax to be stored in the ferroelectric capacitor. A read circuit determines a value stored in the ferroelectric capacitor by measuring a charge stored in the ferroelectric capacitor, measuring Qmax for the ferroelectric capacitor, and determining the data value from the measured charge and the measured Qmax.