Single cell capacitors

Figure 17.16 Hysteresis pulse measurement of a single FeRAM cell capacitor (0.49 /um2 PZT)...

For non-volatile random access memories (NV-RAMs in which the stored information is retained even if power to the chip is interrupted), ferroelectrics serve not just as capacitors (as in the case of the DRAM, described below), but as the memory element itself. Their principal advantages in this application are low-voltage (1.0 V) operation, small size (about 20% of a conventional EEPROM cell - and cost is proportional to size once high-yield production is achieved), radiation hardness (not just for military applications but also for satellite communications systems) and very high speed (60 ns access time in commercial devices, sub-nanosecond in laboratory tests on single cells). 

Tonurist, K., A. Janes, T. Thomberg, H. Kurig, and E. Lust. 2009. Influence of mesopo-rous separator properties on the parameters of electrical double-layer capacitor single cells. Journal of the Electrochemical Society 156 A334-A342. 

The power for the ICD system is supplied by the battery, which serves as the energy storage reservoir. ICDs use either a single-cell battery ( 3V) or two cells in series ( 6.5 V) to charge a high-voltage capacitor up to 750-8(X)V for... 

It is noteworthy that when the single cells are assembled with one electrode as a battery-type electrode and the other as a capacitor-type electrode, as in the case of lead-carbon HUCs, its electrical circuit characteristics is similar to that of conventional electrical capacitors. Accordingly, rip number of lead-carbon HUCs connected in parallel have a voltage similar to that of a single capacitor voltage and the total capacitance is expressed as... 

Therefore the utilization of porous materials with high surface areas serving as electrodes enables capacitors to be made with high capacitance. For example, the use of an activated carbon (10 pF cm ) with the specific surface area of 1000 m g gives a capacitance as high as 100 F g . It should be noted that the capacitance measured in a unit cell corresponds to a quarter of the capacitance per unit weight or volume of the single electrode (F g or F cm ), because the... 

Porous-electrode theory has been used to describe a variety of electrochemical devices including fuel cells, batteries, separation devices, and electrochemical capacitors. In many of these systems, the electrode contains a single solid phase and a single fluid phase. Newman and Tiedemann reviewed the behavior of these flooded porous electrodes [23]. Many fuel-cell electrodes, however, contain more than one fluid phase, which introduces additional complications. Typical fuel cell catalyst layers, for example, contain both an electrolytic phase and a gas phase in addition to the solid electronically conducting phase. An earher review of gas-diffusion electrodes for fuel cells is provided by Bockris and Srinivasan [24]. 

The miniaturized capacitive arrays play a critical role in the development of microsystems in biomedical applications since it can provide much higher sensitivity compared to the single-element capacitive sensor. Each capacitor of capacitance-based membrane sensor array is composed of a stretchable electrode. Satyanarayana et al. introduce a 3 x 3 array of individual sensor unit cells with an area of 1 cm [2]. Tsouti et al. reported a capacitive membrane-based sensor array made up of 256 elements with an area 1.44 cm [3]. Despite the large number of elements, only 32 contacting pad are used to address all the elements. The sensing units of the array have already been described in the capacitive membrane sensor section. The stretchable electrodes of the device are deposited on a silicon membrane and the counter electrode is fabricated... 

Impedance results are commonly fitted to equivalent circuits of resistors and capacitors, such as the Randles circuit shown in Figure 14.1, which is often used to interpret simple electrochemical systems. It describes an electrochemical cell where a single-step Faradaic process in the presence of diffusion may occur. The use of a large-area electrode was particularly important for the impedance measurements since the impedance of a counter electrode must be negligible compared to the impedance of the working electrode [4]. 

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