Topic: Electronic Devices
The following statements are made for FETs:
1. In n-channel depletion mode MOS in the active region, the control voltage $V_{GS}$ is negative.
2. NMOS in depletion mode is cut off for $V_{GS}=0$
3. NMOS in enhance mode is cut off for $V_{GS}=0$
4. There is no path between source and drain in the enhancement mode
Of these, the true statements are
- A. 1 and 2 only
- B. 1 and 3 only
- C. 3 and 4 only
- D. 1, 3 and 4 only
Answer: D. 1, 3 and 4 only
Explanation: In depletion mode, the gate voltage is applied such that the channel length reduces, so in n-channel depletion mode MOSFET, the gate voltage $V_{GS}$ is negative. In depletion mode, the channel between source and drain is present, even at $V_{GS}=0$, $I_{D}\ne 0$ or the MOSFET is not cut-off when $V_{GS}=0$. In enhancement mode, the gate voltage is applied such that to create a channel between the source and drain, as no path exists between source and drain initially. So, n-MOS in enhancement mode is cut-off when $V_{GS}=0$.