What is memristance?

 Memristor adalah properti dari komponen elektronika. Jika muatan mengalir dalam 1 arah melalui rangkaian, resistansi dari komponen akan meningkat dan jika muatan mengalir berlawanan arah dalam rangkaian maka resistansi akan berkurang. Jika aliran muatan berhenti dimatikan menggunakan tegangan maka komponen akan mengingat resistansi terakhir yang dimilikinya dan ketika aliran muatan mulai kembali resistansi rangkaian akan menjadi resistansi saat ia terakhir kali aktif.

Memristance is a property of an electronic component. If charge flows in one direction through a circuit, the resistance of that component of the circuit will increase, and if charge flows in the opposite direction in the circuit, the resistance will decrease. If the flow of charge is stopped by turning off the applied voltage, the component will 'remember' the last resistance that it had, and when the flow of charge starts again the resistance of the circuit will be what it was when it was last active.  Why is memristance important?

 Memristansi menjadi lebih kuat ketika ukuran dirangkaian menjadi lebih kecil. Pada beberapa poin seperti kita menimbang kedalam bidang nano elektronik. Ia akan diperlukan untuk secara eksplisit memperhitungkan memristansi dalam model rangkaian kita dalam rangka mensimulasi dan desain rangkaian elektronik dengan baik.

It turns out that memristance is becoming stronger as the feature sizes in circuits are getting smaller. At some point as we scale into the realm of nanoelectronics, it will be necessary to explicitly take account of memristance in our circuit models in order to simulate and design electronic circuits properly. Have people seen memristance before?

Ya, kita sadar akan lebih 100 paper kembali ke awal tahun 1960 pada saat peneliti mengamati dan melaporkan ketidakbiasaan histeresis dalam plot v-i mereka pada berbagai devais dan rangkaian berdasar pada perbedaan jenis material dan struktur. Dalam tinjauan kebali, kita bisa mengerti bahwa peneliti itu sebenarnya melihat memristansi, tetapi mereka tidak sadar.

 Yes, we are aware of over 100 published papers going back to at least the early 1960's in which researchers observed and reported unusual 'hysteresis' in their current-voltage plots of various devices and circuits based on many different types of materials and structures.  In retrospect, we can understand that those researchers were actually seeing memristance, but they were apparently not aware of it. What is a memristor?

 memristor ideal adalah 2 terminal pasif devais elektronik yang dibangun untuk menyatakan properti memristansi (seperti resistor menyatakan resistansi dan sebuah induktor menyatakan induktansi). Bagaimanapun, dalam paktiknya sangat sulit untuk membuat memristor murni karena real devais mungkin juga memiliki jumlah sedikit dari beberapa properti lain seperi kapasitansi (analogi induktor yang juga memiliki nilai resistansi).

An ideal memristor is a passive two-terminal electronic device that is built to express only the property of memristance (just as a resistor expresses resistance and an inductor expresses inductance). However, in practice it may be difficult to build a 'pure memristor,' since a real device may also have a small amount of some other property, such as capacitance (just as any real inductor also has resistance). What is an analogy for a memristor?

 Analogi utama untuk resistor adalah pipa yang membawa air. Air sendiri dianalogikan sebagai muatan elektrik, tekanan pada input dipipa mirip dengan tegangan. Dan kecepatan aliran air melalui pipa seperti arus listrik. Sama dengan resistor elektrik, aliran air melalui pipa lebih cepat jika pipa lebih pendek dan/atau mempunyai diameter yang besar. Analogi untuk memristor adalah jenis menarik dari pipa yang memperluas atau shrink ketika air mengalir melaluinya. Jika air mengalir melalui pipa dalam satu arah, diameter pipa meningkat, dengan begitu memungkinkanair pada aliran lebih cepat. Jika air mengalir melalui pipa pada arah yang berlawanan, diameter dari pipa akan berkurang, dengan begitu melambatkan aliran air. Jika tekanan air dimatikan, pipa akan mempertahankan diameter terakhir sampai air dinyalakan. Dengan begitu, pipa tidak menyimpan air seperti ember (atau sebuah kapasitor). pipa mengingat berapa banyak air yang telah mengalir melalui nya.

A common analogy for a resistor is a pipe that carries water. The water itself is analogous to electrical charge, the pressure at the input of the pipe is similar to voltage, and the rate of flow of the water through the pipe is like electrical current. Just as with an electrical resistor, the flow of water through the pipe is faster if the pipe is shorter and/or it has a larger diameter. An analogy for a memristor is an interesting kind of pipe that expands or shrinks when water flows through it.  If water flows through the pipe in one direction, the diameter of the pipe increases, thus enabling the water to flow faster. If water flows through the pipe in the opposite direction, the diameter of the pipe decreases, thus slowing down the flow of water. If the water pressure is turned off, the pipe will retain it most recent diameter until the water is turned back on. Thus, the pipe does not store water like a bucket (or a capacitor) – it remembers how much water flowed through it. Who first predicted the existence of memristance and memristors?

 Prof leon chua telah mengubah departement teknik elektro (UC Berkeley) ketika dia mempublikasikan seminal papernya. “memristor- elemen rangkaian yang hilang” . dalam papernya , prof chua membuktikan angka teorema yang menunjukkan bahwa ada yang hilang elemen rangkaian 2 terminal dari keluarga devais pasif dasar (resistor, kapasitor, dan induktor). Dia membuktikan bahwa tidak ada kombinasi dari resistor nonlinear, kapasitor, induktor memungkinkan duplikasi propertis memristor. Tanda yang bisa dikenali dari memristor adalah ketika sebuah tegangan AC digunakan pada devais, (I-V) plot dalam bentuk lissajous (kurva yang dibentuk oleh kombinasi dua osilasi yang perpendikular satu sam lain). ”Yang paling utama observasi melacak “

Prof. Leon Chua had just moved to the Electrical Engineering Department of UC Berkeley when he published his seminal paper, "Memristor - The missing circuit element." IEEE Trans. Circuit TheoryCT-18, 507-519 (1971).  In this paper, Prof. Chua proved a number of theorems to show that there was a 'missing' two-terminal circuit element from the family of "fundamental" passive devices:  resistor, capacitor and inductor (e.g. elements that do not add energy to a circuit). He proved that no combination of nonlinear resistors, capacitors and inductors could duplicate the properties of a memristor.  The most recognizable signature of a memristor is that when an AC voltage is applied to the device, the current-voltage (I-V) plot is a Lissajous figure (the curve formed by combining two oscillations that are perpendicular to each other). The most commonly observed I-V trace is a 'figure 8', or a 'pinched loop' for which the current is zero when the voltage is zero.  This inability to duplicate the properties of a memristor with the other passive circuit elements is what makes the memristor fundamental.  However, this original paper requires a considerable effort for a non-expert to follow. In a later paper, Prof. Chua introduced his 'periodic table' of circuit elements. This was a visually pleasing illustration that we borrowed and modified for our Nature paper on finding memristors.   Aren't there other fundamental passive devices that don't add energy to a circuit? What about diodes?

 

No, there are only four fundamental types of passive circuit elements. Diodes are just non-linear resistors - the resistance of a diode changes with the applied voltage, but if you turn off the voltage and start back at 0 volts, the resistance of the diode is the same as it was before at 0 volts, not what it was when the voltage was turned off. This is also true of a resistor that heats up and increases its resistance because of a temperature increase. Thus, neither a diode nor a heated resistor 'remember' their history. However, each type of fundamental circuit element is actually a family of devices with essentially an infinite number of higher order members. To see all the members of the four families of fundamental devices, see the following paper: Leon O. Chua, "Nonlinear Circuit Foundations for Nanodevices, Part I:  The Four-Element Torus," Proc. IEEE 91, 1830-1859 (2003). This is a very educational paper, but requires a significant investment in effort to appreciate. Note: Part II has not appeared in the literature yet. What was the contribution of HP Labs?

 We were the first to understand that the hysteresis that was being observed in the I-V curves of a wide variety of materials and structures was actually the result of memristance and something more general that can be called 'memristive behavior' [see L.O. Chua & S. M. Kang, "Memristive devices and systems," Proc. IEEE 64, 209-223 (1976)]. We then went on to create an elementary circuit model that was defined by exactly the same mathematical equations as those predicted by Chua for the memristor, with the exception that this model had an upper bound to the resistance (which means that at large bias or long times, it is a memristive device). We then showed that this simple model could reproduce a wide variety of eccentric and complex I-V curves that have been observed and reported over the years by many researchers, including ourselves. Most of these did not look much like the 'figure 8' curves of Chua, but rather 'S' and 'N' curves that have erroneously been attributed to negative differential resistance, which is one reason why the connection to memristive behavior had not been made earlier. We also showed that in a highly simplified form appropriate for a general audience journal like Nature or for a basic undergraduate course, the equations for the drift of oxygen vacancies in TiO2 and their influence on the electronic conduction in the material were also identical with our equivalent circuit model, and thus Chua's memristor equations. From this, we could for the first time write down a formula for the memristance of a device in terms of material and geometrical properties of the device (just as the resistance is the resistivity of the material times the length divided by the cross sectional area of the resistor). Our memristance formula immediately showed that the size of the most important term in the memristance gets larger the smaller the device – thus showing that it was not very important for micron-scale electronics but is becoming very important for nanoscale devices. We have developed more sophisticated and accurate models that will be published at a future date, and we have used our models to design and build better memristors. What types of applications could memristors have?

Kita melihat 2 tipe dari aplikasi untuk memristor dan devais memristif.Pertaman, sebagai nana”{ memori resistor” menyiaratkan untuk tipe NVRAM. Seperti sebuah memori yang mempunyai propertis yang sangat berguna, dalam artian ia akan tidak mengingat data yang ia simpan ketika daya di matikan. Kita memikirkan bahwa NVRAM membuat dengan tipe dari material memristor yang terakhir kali dipelajari oleh banyak grup diseluruh dunia bisa menjadi seorang kompetitor kuat untuk pemasaran flash memori dalam sekitar 5 tahun. Hal yang menarik adalah ketika berbagai metal oxide yang telah diidentifikasi sebagai yang mempunyai fungsi memori yang sanat kompetible dengan fasilitas fabrikasi chip sekarang, jadi mereka bisa dibuat dalam pengecoran logan yang ada tanpa banyak permintaan perubahan. Kontribusi besar dari kerjaan kita untuk effort ini pada point dalam membuat koneksi untuk teori rankaina non linear leon chua- tanpa dasar menerti yan datang dari persamaan rankaiannya, devais itu sendiri tidak berguna.

Aplikasi menarik lainnya adalah “artifisial sinapsis” dalam desain rangkaian untuk komputasi analog. Prof chua menunjukkan koneksi antara propertis dan memristor usulannya dan sebuah sinapsis dalam paper yang pertamanya dan dia telah melakukan banyak penelitian di bidang komputasi saraf. Kami juga berpikir bahwa ini adalah arah penelitian yang sangat menarik dan berpotensi berharga.

Namun, seperti pengalaman menunjukkan, aplikasi yang paling berharga dari memristor kemungkinan besar akan datang dari beberapa mahasiswa muda yang belajar tentang perangkat ini dan memiliki inspirasi untuk sesuatu yang sama sekali baru

 We see two types of applications for memristors and memristive devices. 

The first, as the name "memory resistor" implies, is for a type of non-volatile random access memory, or NVRAM. Such a memory would have very useful properties, in that it would not 'forget' the data that it stores when the power is turned off. We think that NVRAM made with the types of memristor materials that are currently being studied by many groups around the world could be a strong competitor to the flash memory market in about five years. The great thing is that the various metal oxides that have been identified as having a memory function are highly compatible with present chip fabrication facilities, so they can be made in existing foundries without a lot of changes being required. The major contribution of our work to this effort at this point is to make the connection to the non-linear circuit theory of Leon Chua – without the fundamental understanding that comes from his circuit equations, the devices themselves are fairly useless.

Another interesting application is as an 'artificial synapse' in a circuit designed for analog computation.  Prof. Chua himself pointed out the connection between the properties of his proposed memristor and those of a synapse in his earliest papers, and he has performed a lot of research in the area of neural computing. We also think that this is a very interesting and potentially valuable research direction.

However, as experience shows, the most valuable applications of memristors will most likely come from some young student who learns about these devices and has an inspiration for something totally new