Low power consumption, low chip area and fabrication in the standard Complementary Metal Oxide Semiconductor (CMOS) process are vital requirements for oscillators used in low-cost bio-implantable and wearable devices. Conventional ring oscillators (ROs) are good candidates for using in biomedical applications. However, their oscillation frequency strongly depends on the temperature. In this study, a temperature compensated ring oscillator with low power consumption is proposed. The transistors of the proposed ring oscillator operate in the subthreshold region to achieve a low power and low voltage performance. Since, in the subthreshold region, the oscillation frequency of a conventional ring oscillator increases with increase in the temperature, two current sources are used to power the proposed subthreshold ring oscillator: a temperature independent current source and a Complementary to absolute temperature (CTAT) current source. In the proposed circuit, the CTAT current forms a small part of the total supplied current and its duty is to compensate for the oscillation frequency deviation. Two prototypes of the subthreshold ring oscillator were designed and simulated for a target frequency of 1MHz using commercially available 0.18µm RF-CMOS technology. The thermal coefficient (TC) of the uncompensated ring oscillator was 2400 ppm/ºC from -40ºC to 85ºC, though applying the proposed technique reduces the TC of the ring oscillator to 80.4 ppm/ºC with total power consumption as low as 14.5µW.

Bit swapping linear feedback shift register (BS-LFSR) is employed in a conventional linear feedback shirt register (LFSR) to reduce its power dissipation and enhance its performance. In this paper, an enhanced BS-LFSR for low power application is proposed. To achieve low power dissipation, the proposed BS-LFSR introduced the stacking technique to reduce leakage current. In addition, three different architectures to enhance the feedback element used in BS-LFSR was explored. The pass transistor merged with transistor stack method yielded a better reduction in power dissipation compared to pass transistor design and NAND gate design. The BS-LFSR was designed in Mentor Graphic – TSMC Design Kit Environment using 130nm Complementary Metal Oxide Semiconductor (CMOS) technology. The proposed 4-bit BS-LFSR achieved an active area of 1241. 1588um2 and consumed only 53. 8844nW with total power savings of 19. 43%. The proposed design showed superiority when compared with the conventional LFSR and related work in reducing power dissipation and area.

In this work, we study electronic transport properties of a quasi-one dimensional pure semi-conducting Zigzag Carbon Nanotube (CNT) attached to semi-infinite clean Metallic Zigzag CNT leads, taking into account the influence of topological defect in junctions. This structure may behave like a field effect transistor. The calculations are based on the tight-binding model and Green’s function method, in which the local density of states (LDOS) in the Metallic section to semi-conducting section, and muli-channel conductance of the system are calculated in the coherent and linear response regime, numerically. Also we have introduced a circuit model for the system and investigated its current. The theoretical results obtained, can be a base, for developments in designing nano-electronic devices.

Introduction: Megavoltage X-ray beams are used to treat cervix cancer due to their skin-sparing effect. Preferably, the radiation surface doses should be negligible; however, it increases due to electron contamination produced by various field parameters. Therefore, it is essential to provide proper knowledge about the effect of different field parameters on radiation doses. This study sought to find out the effect of various physical parameters on the surface doses. Materials and Methods: The effects of field size, source-to-surface distance, and open or acrylic block tray fields on surface doses were determined. Metal-Oxide-Semiconductor-Field-Effect-Transistor based dosimetric system was used for dose measurements for 6 MV photon beam. The directly measured radiation surface doses on pelvic phantom were compared to surface dose values computed by treatment planning system in the similar field parameters. Results: The measured results for the percentage depth dose (PDD0) in field size of 10x10 cm2 were 13. 32%, 12. 95% and 13. 87% for open field and 36. 87%, 36. 31% and 35. 88% for acrylic block tray field. In addition, the computed doses were 7. 83%, 7. 73% and 7. 65% for open field and 16. 33%, 16. 12% and 15. 88% for acrylic block tray field at 80 cm, 100 cm, and 120 cm SSDs, respectively. Conclusion: The surface dose increases along with the size of the field and decreases with increasing SSD. The surface doses in acrylic block tray fields were significantly higher than the open ones. The treatment planning system computed a lesser radiation doses in same field parameters.