Step 1: Understanding the Concept:
The threshold voltage ($V_{th}$) is the minimum gate-to-source voltage ($V_{GS}$) required to create a conduction channel between the drain and source.
Step 2: Detailed Explanation:
- If $V_{GS}<V_{th}$, the MOSFET is in the cut-off region (no current).
- If $V_{GS}>V_{th}$, the MOSFET turns "ON".
Once the device is ON, it can be in the linear (triode) or saturation region depending on the drain-to-source voltage ($V_{DS}$).
The fundamental condition to even enter the saturation region is that $V_{GS}$ must first exceed $V_{th}$.
Step 3: Final Answer:
The MOSFET requires $V_{GS}>V_{th}$ to operate in the saturation region.