can be taken from the anode to ground from the cathode to ground or differentially across the programmable metallization cell device application_number US 54996406 A description the implementation of the exemplary pmc voltage reference is one example of using pmc as a voltage reference and does not limit the application of the design concept in other circuit configurations for example the voltage reference can be taken from the anode to ground as described below in connection with fig1 from the cathode to ground fig2 or differentially across the pmc device in either case see fig3 and 4 the pmc device is labeled u201c pmc u201d in fig1 and is used in a common anode configuration or the anode voltage is common to other pmc devices in the system the switches s 1 a to s 3 a in fig1 represent solid state switches and could be implemented with transistors the current source inverter and unity gain buffer could also be implemented with common transistor level design to implement the depicted functions in this particular implementation the pmc bias circuit can be enabled as shown in the schematic in fig1 the programming current can be any appropriate value for the system in which the bias circuit is being used typical values would be from 10.