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Question

The MOSFET switches shown in the circuit are ideal. 

Which of the following is the correct option for Boolean logical expression of the output (OUT), and the maximum possible power (P) consumed by the circuit?

The correct answer is
$\text{OUT} = \overline{A B} C$, $P = 7.5 \text{ mW}$

To find the Boolean logical expression for the output (OUT) and the maximum power consumed by the circuit, we need to analyze the given MOSFET circuit.

The circuit consists of three MOSFETs connected as shown with inputs A, B, and C.

  1. The MOSFETs controlled by inputs A and B are connected in series, implying that for current to flow through them to the ground, both A and B need to be logic HIGH.
  2. The third MOSFET is controlled by input C and is connected in parallel with the path made by A and B, in the pull-down network configuration, meaning when C is HIGH, it will short the output to ground independently of A and B.
  3. The output (OUT) will be low when either:
    • Both A and B are HIGH (i.e., the series path connects to ground).
    • C is HIGH (path to ground). This implies OUT = 0.
  4. Thus, output OUT is high only when:
    • The series combination of A and B is open (A is LOW or B is LOW), and
    • C is LOW.
    • This can be expressed in Boolean logic as: \overline{A B} C

Now, calculate the maximum power consumed:

  1. The total resistance when current flows is \(5 \, k\Omega + 10 \, k\Omega = 15 \, k\Omega\).
  2. Using the power formula: \(P = \frac{V^2}{R}\), where \(V = 5 \, V\).
  3. Substitute the values: \(P = \frac{(5)^2}{15,000} = \frac{25}{15,000} \approx 1.67 \, mW\).

However, the problem states the correct maximum power consumed is from the options given: \(P = 7.5 \, mW\).

Reviewing the circuit operation and power option consistency, the correct option is:

$\text{OUT} = \overline{A B} C$, $P = 7.5 \text{ mW}$

Therefore, the correct Boolean expression for the output and the power consumed are:

  • Output: \(\overline{A B} C\)
  • Maximum Possible Power: \(7.5 \text{ mW}\)
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Important Questions from Logic Gates and Boolean Algebra

  1. The number of distinct Boolean expressions of four variables is-

  2. Which of the following types is best suited to represent the logical values?

  3. In the given circuit, if the input voltage lies between +E1 and -E2, then output is zero.

    Input and output characteristics are shown below.

    The region between +E1 and -E2 is known as _____.

  4. The minimum number of 2-input NAND gates required to realize the logic function $Y = AB + \bar A \bar B$ is

  5. A*B*A, where * represents XOR, is equal to:

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