SUMMARYIn this paper the response of a bulk-driven MOS Metal-Oxide-Semiconductor input stage over the input common-mode voltage range is discussed and experimentally evaluated. In particular, the behavior of the effective input transconductance and the input current is studied for different gate bias voltages of the input transistors. A comparison between simulated and measured results, in standard 0.35- §m CMOS Complementary Metal-Oxide-Semiconductor technology, demonstrates that the model of the MOS transistors is not sufficiently accurate for devices operating under forward bias conditions of their sourcebulk pn junction. Therefore, the fabrication and the experimental evaluation of any solution based on this approach are highly recommended. A technique to automatically control the gate bias voltage of a bulk-driven differential pair is proposed to optimize the design tradeoff between the effective input transconductance and the input current. The proposed input stage was integrated as a standalone block and was also included in a 1.5-V second-order operational transconductance amplifier (OTA)-C lowpass filter. Experimental results validate the effectiveness of the approach.

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Rhododendron ponticum subsp. baeticum is endemic in the southern region of the Iberian Peninsula. The relict populations of this species are vulnerable, due mainly to difficult conditions for the establishment of seedlings, resulting in a virtual lack of sexual recruitment. In order to preserve the surviving populations, in vitro culture methods have been applied for both the sexual and the agamic propagation of the species. The in vitro germination of seeds was high when conducted with Anderson's medium without plant growth regulators. The self-rooted seedlings obtained were easily transplanted to outside conditions. The presence of growth regulators in the medium interfered with the development of the seedlings, causing heavy callus formation. The in vitro growth of explants took place readily in Anderson's medium plus 0.072 mg L −1 of BA and 0.036 mg L −1 of NAA although the explants did not form roots. Rooting was achieved by the basal dipping of the explants in hydroalcoholic solutions of 500 mg L −1 IAA during the outside transplanting process. Therefore, the combination of in vitro grown explants together with ex vitro rooting, results in a good method for the agamic propagation of Rhododendron ponticum subsp. baeticum.

This brief introduces four different structures for implementing a continuous-time common-mode feedback (CMFB) network for fully differential (FD) amplifiers. The proposed circuits use bulk-driven MOS transistors, thus representing a lowvoltage realization of their gate-driven counterparts. The CMFB circuits were included in a 1.5-V FD buffer implemented in standard 0.35-µm CMOS technology. Experimental results illustrate the performance of the proposed schemes, demonstrating their suitability to operate with a low supply voltage.

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