fig. 4.20 example 4.5: (a) circuit; (b) analysis whit the steps indicated by the circled numbers.
it follows that the collector-base junction is reverse-biased by 0.7 V and the transistor is indeed in the active mode. the emitter current will be given by/
we note from this example that the collector and emitter currents depend critically on the value of B. in fact, if B were 10% higher, the transistor would leave the active mode and enter saturation. therefore, this clearly is a bad design. the analysis details are illustrated in fig. 4.20(b)./
exercise
D4.17 the circuit of fig. 4.20(a) is to be fabricated a transistor type whose B is specified to be in the range of 50 to 150. (that is, individual units of this same transistor type can have B values anywhere in this range.) redesign the circuit by selecting a new circuit by selecting a new value for Rc so that all fabricated circuits may exhibit?
Ans. Rc = 1.44 k; Vc = 0.7 V to 6.9 V /
example 4.7
we want to analyze the circuit of fig. 4.12(a) to determine the voltages at all nodes and the currents through all branches. Assume B = 100.