Question

A voltage follower
A. has a voltage gain of 1.
B. is non inverting.
C. has no feedback register.
D. has all of these.

Answer 1

Hint: To solve this question, we have to remember that the output voltage of the op-amp exactly tracks the input voltage both in sign and magnitude. This is the reason that this circuit is called a voltage follower or unity gain configuration.

Complete answer:
A voltage follower is an electronic circuit in which output voltage tracks the input voltage both in sign and magnitude.

Because of three unique characteristics of extremely high input resistance, unity transmission gain, and extremely low output resistance, the voltage follower circuit is an ideal circuit device to serve as a buffer. Thus, it can be made to prevent the disturbance of one part of a circuit on another as might be encountered.

In voltage follower,

Output voltage, ${v_{out}} = {v_{in}}$,
From the figure, it is obvious that ${v_2}$ is equal to ${v_{out}}$ and ${v_1}$ is equal to ${v_{in}}$, so
\[
   \Rightarrow {v_{out}} = A{v_d} \\
   \Rightarrow {v_{out}} = A\left( {{v_1} - {v_2}} \right) \\
   \Rightarrow {v_{out}} = A\left( {{v_{in}} - {v_{out}}} \right) \\
\]
Or,
$\dfrac{{{v_{out}}}}{{{v_{in}}}} = \dfrac{A}{{A + 1}} \cong 1$ for A >> 1
Thus, for voltage follower, ${A_f} = 1$
Therefore, we can say that a voltage follower has a voltage gain of 1, is non inverting and has no feedback register.

So, the correct answer is “Option D”.

Note:
The direct connection to the output voltage to the inverting terminal of the op-amp represents the case of 100% negative feedback of the output to the input. Voltage follower is used to increase the input impedance of the system to avoid loading effect.