(a) Replace the BJT of Fig. P2.45 with its smallsignal model, and use the test-signal method to show that the resistance seen looking into the input port is (b) Calculate Ri if RF 5 10 kV, RC 5 1 kV,...

(a) Replace the BJT of Fig. P2.45 with its smallsignal model, and use the test-signal method to show that the resistance seen looking into the input port is

(b) Calculate Ri if RF 5 10 kV, RC 5 1 kV, and the BJT has F 5 100, VA 5 100 V, and is biased at IC 5 1 mA. (c) Discuss the limiting case RF → 0 and RC → `, and justify your result in terms of previously known BJT behavior. (d) Repeat part (c), but in the limiting case RF → `.