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I was studying about amplitude modulation and I found this circuit on the internet.

  • Does anyone know why that ground is needed?

  • Is the first part(three resistors) an adding circuit?

  • Does the diode apply the square law?

circuit

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  • \$\begingroup\$ The diode only allowed the Positive voltages onto the resonator. If moderate bandwidth is implemented, the carrier plus sidebands will be replicated by the stored energy, and the + and the - voltages restored. So yes, seems like the diode non-linearity is needed. Given diodes do not provide squarelaw region (some FETs go), the "modulation" is mostly just distortion, to be filtered by the moderate bandwidth resonator. \$\endgroup\$ – analogsystemsrf Jan 19 at 8:45
  • \$\begingroup\$ Try simulating it. Not only will you learn to use a simulator (very important) but you'll gain intimate knowledge and far more than a short answer can provide. \$\endgroup\$ – Andy aka Jan 19 at 16:31
  • \$\begingroup\$ Thanks guys I searched and found that the resistor in red has a high resistance value. Is it to gain power? And in the material I found something about the non-linear response of the diode can be approached by an e ^ x so I thought it was the squarelaw \$\endgroup\$ – Thiago Baldino Jan 20 at 23:15

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