Figure $18 < 1$ -If $\mathrm { R } _ { f } = 1.2 \mathrm { M } \Omega$

Multiple Choice

Figure $18 < 1$
-If $\mathrm { R } _ { f } = 1.2 \mathrm { M } \Omega$ and A_V=120 in Figure 18-1( c) , Ri equals___________

A) 1 $\mathrm { k } \Omega$
B) 10 $\mathrm { k } \Omega$
C) 120 $\Omega$
D) 100 $\mathrm { k } \Omega$