(a) Assume the simplified small-signal model for transistors shown in Figure 12.5 has $r_i=\infty, g_m=1.8 \times 10^{-3} \mathrm{~S}$, and $r_o=100 \mathrm{k} \Omega$. This device is placed in the circuit as shown in Figure P12.11. Calculate the small-signal voltage gain.
(b) In the amplifier circuit shown in Figure P12.11, calculate the small-signal voltage gain assuming $r_1=200 \mathrm{k} \Omega, g_m=$ $2.5 \times 10^{-3} \mathrm{~S}$, and $r_o=120 \mathrm{k} \Omega$.
Figure P12.11 can't copy