A low drop-out [LDO] voltage regulator with fast transient response which does not require a capacitor for proper operation is proposed in this paper. Recent cap-less LDOs do not use off chip capacitor but instead they use on chip capacitor which occupy a large area on the chip. In the proposed LDO, this on chip capacitor is also avoided. A novel secondary local feedback technique is introduced which helps to achieve a good transient response even in the absence of output capacitor. Further an error amplifier that does need compensation capacitor is selected to reduce the on chip area. Stability analysis shows that the proposed LDO is stable with a phase margin of 78°. The proposed LDO is laid out using Cadence Virtuoso in 180 nm standard CMOS technology. Post layout simulation is carried out and LDO gives 6mV=V and 360µV=mA line and load regulation respectively. An undershoot of 120 mV is observed during the load transition from 0 mA to 50 mA in 1 µs transition time, however LDO is able to recover within 1:4 µs. Since capacitor is not required in any part of design, it occupies only 0:010824 mm2 area on the chip.
The influence of ambient solar UV-A or UV-B radiation on growth responses was investigated in three varieties of cotton (Gossypium hirsutum L.) after exclusion of solar UV-A/B radiation: JK-35, IH-63 and Khandwa-2. Cotton plants were grown from seeds in UV-exclusion chambers lined with selective UV filters to exclude either UV-B (280-315 nm) or UV-A/B (280-400 nm) from the solar spectrum under field conditions. Excluding UV-B and UV-A/B significantly increased plant height, leaf area and dry weight accumulation in all three varieties of cotton. The varieties differed considerably in their sensitivity to ambient UV-A/B. Khandwa-2 was most sensitive and JK-35 least sensitive to ambient solar UV. We monitored the activity of the antioxidant enzymes superoxide dismutase (SOD), ascorbic acid peroxidase (APX), glutathione reductase (GR) and guaiacol peroxidase (GPX), as well as the level of the antioxidant ascorbic acid (ASA), in primary leaves of the most UV-sensitive variety (Khandwa-2). The level of UV-B-absorbing substances was significantly decreased by exclusion of solar UV-B and UV-A/B. Exclusion of solar UV decreased the activity of all the antioxidant enzymes monitored and the level of ascorbic acid versus control plants (+UV-A/B) grown under filters transparent to solar UV. Reduction of the antioxidant defense after UV exclusion indicates that ambient solar UV exerts significant stress and induces some reactive oxygen species to accumulate, which in turn retards the growth and development of cotton plants. Ambient solar UV stresses cotton plants, shifting their metabolism towards defense against solar UV. Exclusion of solar UV eliminates the need for that defense and leads to enhancement of primary metabolism.