Rapid evaluation of the root causes of BJT mismatch

This paper presents a new technique for the simple and rapid evaluation of the process and geometry parameter contributions to BJT mismatch. The pinched base sheet resistance variation, the geometric emitter size variation, and the ideal component of the emitter-base current variation can be uniquely determined from the I_c, I_b and β mismatch variances in the ideal region. The variation in the nonideal component of the base current can be evaluated from the I_b and β mismatch in low level injection region. The variation in extrinsic resistance can be evaluated from the I_c and I_b mismatch in the high current region. The mismatch evaluation can be performed with as few as six measurements per device type per die site.