Design Of Current Reference In Digital TV Tuner

So far, the band-gap reference is the most popular circuit, which successfullyachieves the requirements. It exhibits both high stability and low temperaturecoefficient, also has low noise and simple topology. In this paper, a precise CMOSband-gap current reference which uses first-order curvature compensation isdescribed in detail. Low temperature coefficient and high stability of output currentis the key importance to an ideal current reference. They are also the focus in thispaper.A band-gap reference was designed and provided bias current for the otherpart. The tuner is the very important part in the digital TV receiver system. The keyfunction of the tuner is receiving the RF signal and sending to the modules behind inthe system for demodulation. The temperature related model and the influencingfactor of two band-gap reference devices, sub-threshold MOSFET and PNPsubstrate transistor, based on CMOS process were analyzed and compared, andpointed out that the PNP substrate transistor was more fit for being the band-gapreference device. Choose proper current reference by compared, and analyzed itsparts in detail.The SMIC 0.18um process mix signal model library was choiced for design. Andthe Mentor Eldo simulator was used for the circuits' simulation, Ic-station was usedfor the layout. The results displayed that the temperature coefficient was less than40 ppm/℃at the range of -20℃～80℃, and output current variation of 2uA forsupply voltage range from 1.7 V to 5.0 V. Also the circuit structure of the proposedreference is simple and both chip area and power consumption are small.