Exercise 4 The three terminal device shown in Figure 4(a) is called a bipolar junction transistor (BJT). Figure 4(b) shows a piecewise linear model for the device, in which the parameter 3 is a constant. When iB > 0 and UCEUBE -0.4 the emitter diode behaves like a short circuit, the collector diode like an open circuit, and the collector current is given by ic = BiB Under the above constraints, the BJT is said to operate in its active region. For the rest of this exercise, assume that 3 = 100. B iB VBE (a) iE E VCE B iB 0.4 V |||| VBE ic BiB E E VCE 0.6 V (b) Figure 4: (a) A bipolar junction transistor. B stands for base, E for emitter and C for collector. (b) A piecewise linear model for the BJT a) Determine the collector current ic for a base current i = 1μA and vCE = 2V using the model in Figure 4(b). b) Sketch a graph of ic versus UCE for ip = 1µA. using the model in Figure 4(b). In drawing this graph, assume that the current source turns off for UCE UBE-0.4

Exercise 4 The three terminal device shown in Figure 4(a) is called a bipolar junction transistor (BJT). Figure 4(b) shows a piecewise linear model for the device, in which the parameter 3 is a constant. When iB > 0 and UCEUBE -0.4 the emitter diode behaves like a short circuit, the collector diode like an open circuit, and the collector current is given by ic = BiB Under the above constraints, the BJT is said to operate in its active region. For the rest of this exercise, assume that 3 = 100. B iB VBE (a) iE E VCE B iB 0.4 V |||| VBE ic BiB E E VCE 0.6 V (b) Figure 4: (a) A bipolar junction transistor. B stands for base, E for emitter and C for collector. (b) A piecewise linear model for the BJT a) Determine the collector current ic for a base current i = 1μA and vCE = 2V using the model in Figure 4(b). b) Sketch a graph of ic versus UCE for ip = 1µA. using the model in Figure 4(b). In drawing this graph, assume that the current source turns off for UCE UBE-0.4