Consider an npn bipolar junction transistor (BJT) having step junctions with the properties in Table Q4. NAB= 4 x 1017 cm-3 DPE = 3.7 cm/s VEB = 0.8 V (forward bias) Table Q4 WB = 0.13 m DnB = 12 cm/s VCB = 2 V (reverse bias) WE = 0.2 m a) Calculate the dopant concentration of NDE if the current gain in common emitter, is 300. Using the calculated value, estimate the maximum metallurgical base width, WBM in the npn BJT. b) Illustrate the energy band diagram of the npn BJT.