Response to the following problem:
Consider a transistor for which the base-emitter voltage drop is 0.7 V at 10 mA. What current flows for vBE= 0.5 V? Evaluate the ratio of the slopes of the iC-vBE curve at Vbe 700 mV and at vBE = 500 mV. The large ratio confirms the point that the BJT has an "apparent threshold" at vB 0.5 V.