I have a problem understanding the circuit below where the LC oscillator is used to produce the negative cycle wave for the amplitude modulation.

I am having a difficulty in grasping the fact that the oscillator produces the negative cycle. Does the LC get a pulse from the half wave and then this pulse is converted to sine form?

enter image description here

Secondly, I have my carrier wave given to the signal but with the changing values of the LC my frequency should change accordingly. Should I choose a value of the oscillation equal to the resonant frequency?

  • 1
    \$\begingroup\$ The "LC" is not an oscillator; it's a tuned circuit (sometimes referred to as a tank). The value of the LC doesn't change and, accordingly, the frequency should not change either. The clue is in the phrase "amplitude modulation" and not frequency modulation. \$\endgroup\$
    – Andy aka
    Commented Oct 23, 2023 at 9:13
  • \$\begingroup\$ But how does it generate the nagitive cycle when the rectifier makes it positive \$\endgroup\$
    – kam1212
    Commented Oct 23, 2023 at 9:22
  • \$\begingroup\$ @Andyaka by. Changing the values I mean that changing the values of the LC changes the results and the output wave. What does the values depend on.? \$\endgroup\$
    – kam1212
    Commented Oct 23, 2023 at 9:29
  • \$\begingroup\$ There does seem to be some confusion, (and maybe a few things are being mixed up too). What is the given part of your question - the two frequencies or the two LC components? Did you calculate the resonant frequency of the existing LC components? Was it a frequency of interest? \$\endgroup\$
    – Nedd
    Commented Oct 23, 2023 at 11:19
  • \$\begingroup\$ @Nedd I meant that how do we select the two LC components value?? Also what's the concept behind using an LC tank here?? I am not getting it conceptually \$\endgroup\$
    – kam1212
    Commented Oct 23, 2023 at 11:43

1 Answer 1


AM modulation in the simplest way is done like this: enter image description here


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