Which of the following statements are correct for an N channel FETs?
A. N channel FET has larger electron mobility than P channel FETs.
B. N channel FET has electrons as current carriers.
C. N channel FET has more noise than P channel FET.
D. N channel FET has larger transconductance than P channel FETs.
Choose the correct answer from the options given below:
Understanding N Channel FET Characteristics
This question asks us to identify the correct statements about N-channel Field-Effect Transistors (FETs) in comparison to P-channel FETs. Let's analyze each statement:
Statement A: N channel FET has larger electron mobility than P channel FETs.
Analysis: This statement is correct. In semiconductor physics, electrons have significantly higher mobility compared to holes. Since N-channel FETs use electrons as their majority charge carriers, and P-channel FETs use holes, the N-channel variant benefits from this mobility difference.
Statement B: N channel FET has electrons as current carriers.
Analysis: This statement is correct. By definition, an N-channel FET (or NMOS) is a type of FET where the majority carriers responsible for conducting current through the channel are electrons. Conversely, a P-channel FET (PMOS) uses holes as majority carriers.
Statement C: N channel FET has more noise than P channel FET.
Analysis: This statement is generally considered incorrect. P-channel FETs (PMOS) typically exhibit lower noise levels, particularly lower flicker noise (1/f noise), compared to N-channel FETs (NMOS). This is often attributed to the lower hole mobility and different interface trap dynamics in PMOS devices.
Statement D: N channel FET has larger transconductance than P channel FETs.
Analysis: This statement is correct. Transconductance ($g_m$) is a measure of how effectively the gate voltage controls the drain current. Since electron mobility is higher than hole mobility, N-channel FETs generally achieve higher transconductance values than P-channel FETs under similar operating conditions and device geometries. The transconductance is directly proportional to the carrier mobility ($\mu$) and other factors like the overdrive voltage ($V_{GS} - V_{th}$) and device dimensions ($W/L$), so higher mobility leads to higher $g_m$. Mathematically, for a MOSFET in saturation, $g_m \approx \mu C_{ox} \frac{W}{L} (V_{GS} - V_{th})$, where $\mu$ is the carrier mobility.
Conclusion on Correct Statements
Based on the analysis, the correct statements regarding N-channel FETs are A, B, and D.
- Statement A is true due to higher electron mobility.
- Statement B is true by the definition of N-channel devices.
- Statement C is false as PMOS usually has less noise.
- Statement D is true due to the higher electron mobility leading to greater transconductance.
Therefore, the combination representing the correct statements is A, B, and D.
Important Questions from Operation of JFET
A junction Field Effect Transistor can operate in
In a junction field effect transistor the depletion layer width at a distance x from the source is:
- The ohmic resistance of JFET with $V_p = 4V$ and $I_{DSS} = 10mA$ is
For a JFET, above the pinch-off voltage, as the drain voltage increases, the
List – I (Structure/Characteristics) List – II (Reasons) a. n-channel JFET is better than p-channel JFET i. Reverse bias increases along the channel b. Channel is wedge shaped ii. High electric field near the drain and directed towards source c. Channel is not completely closed at pinch-off iii. Low leakage current at the gate terminal d. Input impedance is high iv. Better frequency performance since μn >> μp Codes :
