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For an n-channel MOS transistor with $\mu_n$ = 600 cm2/Vs, Cox = 7 x 10-8  F/cm2, W = 40 $\mu_m$, L = 4$\mu_m$ and VTO=1.0 V, the value of K parameter is:

This question was previously asked in
UGC NET 2023 Electronic Science Question Paper (13-Dec-2023) (Shift 1)
The correct answer is

42 x 10-5  A/V2

To solve for the value of the transconductance parameter \( K \) for the given n-channel MOSFET, we use the formula:

\(K = \frac{\mu_n \cdot C_{ox} \cdot W}{2L}\)

where:

  • \(\mu_n\) = electron mobility = 600 cm2/Vs
  • \(C_{ox}\) = oxide capacitance per unit area = \(7 \times 10^{-8}\) F/cm2
  • \(W\) = width = 40 μm = \(40 \times 10^{-4}\) cm
  • \(L\) = channel length = 4 μm = \(4 \times 10^{-4}\) cm

Substituting the known values into the formula:

\(K = \frac{600 \cdot (7 \times 10^{-8}) \cdot (40 \times 10^{-4})}{2 \times (4 \times 10^{-4})}\)

First, calculate the numerator:

\(600 \cdot 7 \cdot 40 = 168000\)
Therefore, the numerator is \(168000 \times 10^{-8} \times 10^{-4} = 168000 \times 10^{-12}\)

Calculate the denominator:

\(2 \cdot 4 \times 10^{-4} = 8 \times 10^{-4}\)

Now divide the numerator by the denominator:

\(K = \frac{168000 \times 10^{-12}}{8 \times 10^{-4}} = \frac{168000}{8} \times 10^{-8} = 21000 \times 10^{-8}\)

Simplifying further, we get:

\(21000 \times 10^{-8} = 2.1 \times 10^{-4} = 42 \times 10^{-5} \text{ A/V}^2\)

Thus, the value of the \(K\) parameter is 42 x 10-5  A/V2.

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Important Questions from MOSFET

  1. An n-channel MOSFET is connected as shown in the Figure.
    Assume $V_{TH} = 1\text{ V}$, $V_{DD} = 5\text{ V}$, and $\mu C_{ox}\left(\frac{W}{L}\right) = 2\text{ mA V}^{-2}$ and neglect channel length modulation effects.
    The gate voltage ($V_G$) of the n-channel MOSFET (in Volt) is __.
    (rounded off to two decimal places)

  2. A semiconductor uses P-type substrates with $N_A = 5 \times 10^{15}cm^{-3}$ in an n-MOS device having depletion region width of 0.415 $\mu$m. What is the depletion charge in magnitude?
  3. MOSFETs exhibit a non-linear relationship between input voltage and output current due to the device construction. The non-linear relationship is connected through the device parameter 'K'. Calculate 'K' for a specific MOSFET operating with an input voltage of 6 V and output current of 10 mA. The Threshold voltage of the chosen MOSFET is 4 V.
  4. Given below are two statements: one is labelled as Assertion (a) and the other is labelled as Reason (r).
    Assertion (a): In a ratioless logic, the transistors can be of minimum size.
    Reason (r): In a ratioless logic, the logic levels are not dependent upon the relative device size.
  5. What are the effects of increasing temperature in the I-V characteristics of the NMOS transistor ?
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