1. A programmable non-volatile analog voltage source comprising, in a single integrated circuit: a pair of electrically erasable floating gate differential analog voltage storage cells for storing an analog voltage as a difference between a pair of voltages stored in the differential analog voltage storage cells, and for providing as an output at least one analog voltage output in response thereto; buffer means responsive to the output of the differential analog voltage storage cells to provide a low impedance analog output in response thereto; and, write means responsive to a write signal to cause an analog voltage input to be stored in the pair of electrically erasable floating gate differential analog voltage storage cells.