JEE Main & Advanced AIEEE Solved Paper-2013

  • question_answer
    A diode detector is used to detect an amplitude modulated wave of 60% modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.     AIEEE Solevd Paper-2013

    A) 10.62 MHz                          

    B) 10.62 kHz            

    C)        5.31 MHz

    D)                       5.31 kHz

    Correct Answer: D

    Solution :

    Cut−off frequency is given by \[{{f}_{c}}=\frac{1}{2\pi RC}\] \[=\frac{1}{2\times 3.14\times {{10}^{5}}\times 250\times {{10}^{-12}}}\] \[=6.37\text{ }KHZ.\] Modulation factor\[=\frac{\sqrt{1-{{m}^{2}}}}{m}\]             \[(n=0.6)\] \[=\frac{4}{3}\] So, maximum frequency that can be detected should be less than modulation factor\[\times \text{ }{{f}_{c}}\] i.e., Less than\[6.37\times \frac{4}{3}=8.5\,KH\] \[\therefore \]Option (4) is correct.


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