Free help with homework

Why join Brainly?

  • ask questions about your assignment
  • get answers with explanations
  • find similar questions

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 100000ohm.Find the maximum modulated frequency which would be detected
Answer is10.62k Hz
Plz solve the problem in easy method



This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
Diode detector for AM signal: 
     this is a low pass filter, removing the carrier frequency and giving back the envelope.

     In a diode (tunnel diode) detector for amplitude modulation, we use a diode in series with the AM signal.  Then to the output of the diode, a parallel combination of a resistor R and a capacitor (condenser) C  are connected.  The other end of R and C are grounded.
     The voltage or current signal at the R and C is the envelope of the modulated signal, which is the demodulated message (audio) signal.

     ω_c = carrier frequency (angular)  = 2 π f_c
     ω_m = audio signal frequency  (angular) = 2 π f_m

We choose RC time constant such that :
        ω_c > 1/RC  > ω_m
         f_c  >  1/(2πRC)  > f_m
         f_c >  1/(2π*250*10⁻¹² * 10⁵)    >  f_m
         f_c  >  6366.2 Hz > f_m

If the input signal is modulated to 100%  (amplitude of the modulating audio signal divided by carrier amplitude), then the above are the limiting frequencies.

 If the AM signal is modulated by a modulating factor = mf  < 1, then

         f_c >  1/(2πRC)  * 1/mf  > f_m
         f_c > 6, 366.2 *  100/60  > f_m
           f_c  >  10, 610.3 Hz  > f_m

maximum audio frequency detectable = 10.6103 kHz
the carrier frequency must be more than  10.6103 kHz

1 5 1
The Brain
  • The Brain
  • Helper
Not sure about the answer?
Learn more with Brainly!
Having trouble with your homework?
Get free help!
  • 80% of questions are answered in under 10 minutes
  • Answers come with explanations, so that you can learn
  • Answer quality is ensured by our experts