On chip measurement of I/sub C/(V/sub BE/) characteristics for high accuracy bandgap applications

The E/sub G/ and X/sub TI/ coefficients are sufficient to completely characterise the temperature dependence of I/sub C/(V/sub BE/) relationship of bipolar transistors (BJT). They are usually obtained from measured V/sub BE/(T) values, using least square algorithm at a constant collector current. This method involves an accurate measurement of V/sub BE/ and of the operating temperature. We propose in this paper, a configurable test structure dedicated to the extraction of the temperature dependence of I/sub C/(V/sub BE/) characteristic for the BJT designed with bipolar or BiCMOS processes. This allows a direct measurement of the die temperature and consequently an accurate measurement of V/sub BE/(T). First, the classical extraction method is explained. Then, the implementation technique of the new method is discussed and finally, an improvement of a bandgap design is presented.