Q.What do you understand by unity follower? Explain its gain term with a neat circuit diagram.

A unity follower (voltage follower) is a non-inverting amplifier in which the whole output is fed back to the inverting input, giving a gain of one. …

[!TLDR]

A unity follower ties the output to the inverting input, giving $A_v = 1$ and $V_o = V_{in}$, with high input and low output impedance.

Circuit: the input signal $V_{in}$ drives the non-inverting (+) input, and the output is connected straight back to the inverting (−) input — there is no input resistor and no separate feedback resistor.

Gain: starting from the non-inverting gain $A_v = 1 + R_f/R_1$, setting $R_f = 0$ (direct feedback) and $R_1 = \infty$ (open) gives $A_v = 1$. Since the differential input voltage is zero, the inverting input follows the non-inverting input, so $V_o = V_{in}$. …