Let the BJT of have VBE(sat) 5 0.7 V, VCE(EOS) 5 0.2 V, VCE(sat) 5 0.1 V, and F 5 75. Moreover, let VCC 5 5V, VBB 5 22 V, R1 5 10 kV, R2 5 20 kV, and RC 5 1.2 kV. (a) If vS, after having been at 5 V...

Let the BJT of have VBE(sat) 5 0.7 V, VCE(EOS) 5 0.2 V, VCE(sat) 5 0.1 V, and F 5 75. Moreover, let VCC 5 5V, VBB 5 22 V, R1 5 10 kV, R2 5 20 kV, and RC 5 1.2 kV. (a) If vS, after having been at 5 V for a long time, is switched to 0 V and the storage time is tS 5 30 ns, fi nd the time constant S. (b) We can make tS → 0 by adding a capacitance C as in Fig. P6.53b and adjusting it to the value CEOS that, as vS switches from 5 V to 0 V, will pull out of the base the charge QS needed to bring the BJT right to the EOS. What is the required CEOS? (c) Find tS if C is made equal to CEOSy2.