$-8\mathrm{.}61$ For the current mirror in Fig. P$8\mathrm{.}61,$ derive an expression for the current transfer function $I_a\frac{s}{I_i}(s)$ taking into account the BJT internal capacitances and neglecting $r_x$ and $r_0.$ Assume the BJTs to be identical. Observe that a signal ground appears at the collector of $Q_2.$ If the mirror is biased at $1$ mA and the BJTs at this operating point are characterized by $f_T=400MHz,C_{}=2pF,$ and ${}_0=,$ find the frequencies of the pole and zero of the transfer function.