In this paper, novel carbon nanotube (CNT) based operational transconductance amplifiers (OTAs) have been designed and simulated. Three types of CNT-based OTAs have been designed at 45 nm technology node and have been compared with the conventional CMOS-based OTA. The comparative analysis of the key characteristics of all the devices has revealed that a significant improvement in performance is observed in the CNT-based OTAs, particularly in a pure CNT-OTA. In the pure CNT-OTA, DC gain has increased by 218%, slew rate has increased by 22.58%, the output resistance has increased by 55.2% and the power consumption is ∼ 193 times less in comparison to the conventional CMOS-OTA. Further, common mode rejection ratio (CMRR) and power supply rejection ratio positive (PSRR+) has increased by 31.87% and 136.3%, respectively in pure CNT-OTA. The performance of CNT-based OTAs has also been studied thoroughly by varying the number of CNTs (N), CNT pitch (S) and the diameter of CNTs (D CNT ) at 0.9 V. It has been observed that their performance can be improved further by using optimized values of CNT number; inter CNT-pitch and diameter. The stability analysis has shown that the pure CNT-OTA is highly stable. A 16.7% and 4% increase in phase and gain margins is achieved in the pure CNT-OTA in comparison to the bulk CMOS OTA. Finally, band and high pass filters have been realized by using the proposed CNT-based OTAs.

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Hydrothermally synthesized TiO 2 nanotubes (TNTs) with a diameter of approximately 10 nm and a length of 250 nm are successfully employed in dye-sensitized solar cells (DSSCs) based on N719 dye and iodide/ triiodide electrolyte and exhibiting an efficiency of 7.6% at 1 sun illumination. Randomly oriented TiO 2 nanotubes are deposited on FTO glass by the electrophoretic deposition method, and the thickness of the TNT layer and hence the solar cell performance have been shown to depend on the deposition time and the nanotube concentration in the electrolyte solution. The highest efficiency is obtained for the solar cell fabricated with the 6-minute electrophoretically deposited TiO 2 film having a film thickness of $6 mm. These pristine TNT photoelectrodes exhibit a short-circuit current density (J sc ), an open-circuit voltage (V oc ), a fill factor (FF) and an efficiency (h) of 2.4 mA cm À2 , 899 mV, 78% and 1.7%, respectively. TiCl 4 treatment of pristine TNT photoelectrodes enhances the J sc , V oc , FF and h to 13.2 mA cm À2 , 819 mV, 70.4% and 7.6%, respectively. The TiCl 4 treatment is found to be vital for the enhancement of the solar cell performance of hydrothermally synthesised TiO 2 nanotube based devices. Enhancement of electron lifetime is noted after treatment of bare TiO 2 nanotubes with 0.5 M TiCl 4 solution. The electron transport resistance, electron lifetime and charge recombination properties of bare and TiCl 4 treated TiO 2 nanotubes are investigated by electrochemical impedance measurements. The increased performance of the DSSC fabricated with TiCl 4 treated TNTs is due to several factors favouring the enhancement of efficiency. These include the dye loading amount, the decrease in electron transport resistance, the increase in density of states and enhancement of light scattering.

In this paper, we design and implement a set of Walsh transform and inverse Walsh transforms for signal processing. The Walsh and inverse Walsh transforms are designed to produce correct results for any input data combinations by providing sufficient word lengths at every steps of the design. Addition, subtraction and dyadic convolution processes have been chosen to demonstrate the performance of the designs. Detail word lengths designs in order to minimize the circuits are presented. It is found that the proposed Walsh transform structure is superior to many of the reported results when it is implemented on FPGAs in terms of area and speed.