The Research And Design Of High Linearity Low Power OTA And Filter

With the performance improving and the market expanding of battery power portable electronic products, such as mobile communication products, wearable products, portable biomedical products, etc, how to reduce the power consumption of the chip become more and more important problem. Therefor, low-power analog IC design techniques have become very necessary and significant. Analog filter is one of the important building blocks in signal processing circuit. Thus,the research on the design of low-power analog filter is very helpful to the analog IC design. This paper maily studies on OTA-C filter has been widely used.The thesis has done the widespread investigation about low-voltage low-power analog IC design and through analyzing and evaluating the performance of these technologies, we use the sub-threshold region as a focus of our low-power syudy in this paper. Then we study the principle of transconductance amplifier and analyze its dc characteristics in saturated region and sub-threshold region and know that the relationship of output current and differential input voltage of OTA is the hyperbolic tangent function. On this basis, we solve the problem that input linear range is too small in sub-threshold region.This paper enhanced the input linearity of OTA with four technologies: bulk driven, two feedback techniques known as source degeneration and gate degeneration and a novel bump-linearization technique. Bulk driven also can effectively reduce the power supply voltage and provide a free gate terminal to do feedback. The structure of bump circuit is that increase a branch contained two transistors in the middle of two branches of differential pair. This structure can effectively improve input linearity, which have the relationship of hyperbolic tangent function like the case of sub-threshold region. The four techniques also reduce the conductance gain and make dc gain too small. Therefor, this paper proposed an improved current mirror as the output stage to enhance the output impedance and to get more dc gain. Besides,this new current mirror is also suitable for low-voltage applications. Finally, we apply this OTA to the filter and get a low-voltage,low-power filter with a large input swing.All circuit designs in this paper use standard model parameters for 0.18 ?m CMOS fabrication process. The circuit is designed by using Virtuoso Schematic Composer and simulated by using Analog Design Environment on Cadence. Simulation results show that, when operated under 0.9V supply voltage, the proposed OTA's dc gain can reach more than 40 d B, its-3d B bandwidth is about 55 k Hz, its input linear range improves from a few millivolt to ?1V and only consumes 110 n W of power. The OTA-C filter composed of OTA is good in performance,its pass band is flat, stop-band attenuation rapidly and its Cut-off frequency is about 600 Hz, the input swing may reach 0.8V. besides,it only has less than 400 n W power dissipation. In a word, the design of OTA and its OTA-C filter in this paper meets our requirement of large linearity and low-power. As a general module, the OTA and OTA-C filter designed in this paper can be play a key role in the low-power design of analog integrated circuits.