(a) In the Sziklai circuit of Fig. P4.24 replace each BJT with its small-signal model and use the test-signal method to obtain an expression for the ac resistance seen looking into each terminal of...

(a) In the Sziklai circuit of Fig. P4.24 replace each BJT with its small-signal model and use the test-signal method to obtain an expression for the ac resistance seen looking into each terminal of the composite device if the other two terminals are at ac ground. (b) Assuming 2 5 100 and VA1 5 VA2 5 100 V, calculate the above resistances if IC2 5 1 mA and I 5 90 A. Comment on your results and compare with the conventional Darlington circuit of Fig. 4.32b.