9.49 (a) For the amplifier circuit in Example 9.6, find the
expression for τ H using symbols (as opposed to numbers).
(b) For the same circuit, use the approximate method of the
previous section to determine an expression for Cin and
hence the effective time constant τ = Cin R′sig that can be
used to find ωH as 1 ⁄ τ . Compare this expression of τ with
that of τH in (a). What is the difference? Compute the value
of the difference and express it as a percentage of τ.