(a) A bipolar cascode is implemented with BJTs having gm 5 1y(25 V), r5 2.5 kV, and ro 5 50 kV (for simplicity assume r5 `). Draw its ac equivalent by replacing each BJT with its small-signal...

(a) A bipolar cascode is implemented with BJTs having gm 5 1y(25 V), r5 2.5 kV, and ro 5 50 kV (for simplicity assume r5 `). Draw its ac equivalent by replacing each BJT with its small-signal equivalent, and fi nd all voltages and currents in the circuit for the case in which vi has been adjusted for vbe2 5 1 mV. Check your results by verifying that KCL is satisfi ed at vc1 and vo. (b) Find the output load RL that will reduce vo to 1 ⁄2 the value of part (a) for the same value of vi , and check again via KCL.