We all know that the basic building block of any communication system is the reference voltage generator. The objective of reference generation is to establish a DC voltage or current that is independent of the supply and process and has a well-defined behavior with temperature. Band Gap Reference (BGR) is one of the most popular reference generators. In the conventional BGR circuit, the reference voltage Vref is the summation of thermal voltage VT and the base to emitter voltage of a transistor (Vf). The thermal voltage VT has a (+Ve) temperature coefficient (TC), whereas Vf has a (-Ve) temperature coefficient (TC). So BGR is independent of temperature . The traditional BGR circuit generates a reference voltage about 1. 12V. So this circuit limits a low supply-voltage operation below 1v. In this paper a new BGR circuit in 0. 25?m iCMOS technology, and a new BGR in BiCMOS technology is proposed which are containing a extra (-ve) feedback loop to get very low reference voltage as well as to stabilize this reference voltage even when it is operating below 1v supply. The TC of this reference generator is getting even zero by applying a (-ve) feedback loop. For a temperature variation between -400 C and 1000 C,the BGR of CMOS technology, and for a temperature variation between -400 C and 600 C, the BGR of BiCMOS technology, the produced reference voltages are absolutely independent of temperature variation together with the capability of operating at very low supply voltage (less than 1V).

CMOS Band