9.71 Consider an active-loaded common-emitter amplifier.
Let the amplifier be fed with an ideal voltage source Vi, and
neglect the effect of rx. Assume that the bias current source has
a very high resistance and that there is a capacitance CL present
between the output node and ground. This capacitance represents
the sum of the input capacitance of the subsequent stage
and the inevitable parasitic capacitance between collector and
ground. Show that the voltage gain is given by