Memristor Emulators: a Note on Modeling

In a recent publication (Yi et al. 2011) elucidating a possible scheme to write information reliably onto a memory crossbar,Hewlett Packard Labs researchers employed a thyristor-based circuit to emulate the off-to-on switching behaviour of a titanium oxide memristor. The use of a thyristor device allowed them to test inexpensively and reliably the functionalities of the closed-loop crossbar write circuitry by using conventional CMOS components. From a device modeling point of view, however, it is worthy to point out that the aforementioned emulator is not a genuine memristor. The aim of this paper is to demonstrate with an in-depth mathematical analysis that the model of the thyristor does not fall into the class of memristors. The modelling approach adopted in this work may be a source of inspiration for researchers willing to check whether other devices or circuits may be classified as memristors.