For the circuit in Figure $18-9,Vf$ is equal to:

A$)B{V}_{\text{o}\text{u}\text{t}}$

B$)(\frac{R_i}{R_i+R_f})V_{\text{o}\text{u}\text{t}}$

C$)V_{in}$

D$)$ all of the above

For the circuit in Figure $18-9,$ what is the approximate closed$-$loop voltage gain $A_{cl}$ of the circuit?

A$)A_{cl}$ cannot be determined without knowing the actual values of $R_i,R_f,$ and $A_{0l}$

B$)(1+\frac{R_i}{?})$

C$)\{1+\frac{R_f}{?}\}$

D$)\{\frac{R_i}{}\}{A}_{ol}$

For Figure $18-8,$ which circuit does not use negative feedback?

A$)$ A

B$)$ B

C$)$ C

D$)$ The circuits all use negative feedback

For Figure $18-8,$ what type of circuit does circuit A represent?

A$)$ Inverting amplifier

B$)$ Voltage follower

C$)$ Non$-$inverting amplifier

D$)$ None of the above