JEE Main 2013PhysicsSemiconductorsHardMCQ

JEE Main 2013 — Semiconductors Question with Solution

JEE Main 2013 (07 Apr)

Question

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 of 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.

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Show full solutionCorrect option: D
Correct answer
D 10.62 kHz

Step-by-step explanation



τ = RC = 1 0 0 × 1 0 3 × 2 5 0 × 1 0 - 1 2  sec

           = 2.5 × 1 0 7 × 1 0 -1 2  sec
 
            = 2.5 × 1 0 - 5  sec

The higher frequency which can be detected with tolerable distortion is

f = 1 2 π m a RC = 1 2 π × 0.6 × 2.5 × 1 0 - 5  Hz

  =100×10425×1.2π  Hz

   = 4 1.2 π × 1 0 4  Hz

   =  10.61 kHz

This condition is obtained by applying the condition that rate of decay of capacitor voltage must be equal or less then the rate of decay modulated signal voltage for proper detection of modulated signal.

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About this question

This is a previous-year question from JEE Main 2013, covering the Semiconductors chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.