Problem:   Calculate the resistance at -37.5 mA

Solution:

· Draw in tangent line at -37.5 mA

· Identify slope points

o at intersections of horizontal and vertical grid lines

o 80 mA, 4.6V

o -100 mA, -3.2V

· Calculate slope:                                               V = R  I

Slope = Δy /Δx  = ΔV /ΔI                     y = m  x  +  b     

o R = (4.6 - -3.2)V / (0.08 – -0.1)A

o Resistance = 43.3 Ω

(Note, this is between hot dynamic and cold dynamic, closer to hot dynamic.  Hot dynamic is NOT requested by your lab)

Cold ~ is tangent line in the region of -10 mA to +10 mA

Hot ~ is tangent line in regions of either ± (60 mA to 100 mA)

Cold dynamic ~ is a tangent line in the regions of either ± (15 mA to 25 mA)