# Source Follower Revisited

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This exercise is a continuation of the previous exercise.

As a reminder:

This problem studies the MOSFET amplifier shown below. Assume that the MOSFET operates in its saturation region, defined by i_D = 0.5K \left( v_{GS} − V_T \right)^2 and 0 \leq v_{GS} − V_T \leq v_{DS}.

You previously generated an expression for v_{OUT}, assuming that the MOSFET operates in its saturation region.

Now:

###Part 1

Determine the range of v_{IN} over which the MOSFET operates in its saturation region. Express your answers in terms of `VS`

, `VT`

, `R`

, `K`

, and regular math operators as needed.

Lower Limit = | |

Upper Limit = |

###Part 2
Determine the small-signal gain of the amplifier assuming that the MOSFET operates in its
saturation region. Use `vIN`

, `VT`

, `R`

, `K`

, and regular math operators as needed.

###Part 3 Consider the case in which 2RK(v_{\text{IN}} - V_{\text{T}}) \gg 1. For this case, approximate the small-signal gain of the amplifier.

Use `vIN`

for v_{\text{IN}}, `VT`

for V_{\text{T}} as needed.