Refer to Problem 10.22. Assume ? = 7,000. Find the allowable range of RB.
Problem 10.22
Consider the LED driver circuit of Figure 10.17. This circuit is now used to drive an automotive fuel injector (an electromechanical solenoid valve). The differences in the circuit are as follows: The collector resistor and the LED are replaced by the fuel injector, which can be modeled as a series RL circuit. The voltage supply for the fuel injector is 13 V (instead of 5 V). For the purposes of this problem, it is reasonable to assume R = 12 ? and L ? 0. Assume that the maximum current that can be supplied by the microprocessor is 1 mA, that the current required to drive the fuel injector must be at least 1 A, and that the transistor saturation voltage is VCEsat = 1 V. Find the minimum value of ? required for the transistor.
Analysis:
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