Examining the output characteristic curves of Figure 3-9, we note that the curves get steeper as the current level increases. In fact, if these lines are extended to the left, they are supposed to meet and intersect the VCE axis at exactly the same point, as illustrated in Figure 3-10. This point, commonly denoted as Vu, is referred to as the Early voltage after J. M. Early, who discovered this and other characteristics of the transistor. The Early voltage is a useful transistor parameter that will be utilized later in the analysis and design of transistor circuits.