Amplitude Modulator


Modulation is a technique in which message signal is transmitted to the receiver with the help of carrier signal. Here in modulation, we combine both carrier signal and message signal. You may get the doubt that what is the need of modulation. Just imagine that you have a paper which contains the message and you would like to send it to your friend standing 40 feet from your place. You can’t just through the paper to your friend because paper will not travel that much distance but if you take small stone and cover the paper with it and through it to your friend, it will definitely reach the target. In the same way, we need a carrier signal to transmit our message. Sometimes, message signal is also called as modulating signal. The exact definition of modulation is given below:

“Modulation is a process of message signal and modulating is varied according to the carrier signal for transmission purpose. The message signal can varied in accordance to the carrier signal that is in terms of angular or amplitude. So we are modulating the signal.”

Amplitude Modulation:

In the amplitude modulation, amplitude of carrier signal wave is varied in accordance with the modulating or message signal by keeping the phase and frequency of the signals constant. The carrier signal frequency would be greater than the modulating signal frequency. Amplitude modulation is first type of modulation used for transmitting messages for long distances by the mankind. The AM radio ranges in between 535 to 1705 kHz which is great.

Circuit Diagram:

Circuit_Amplitude Modulation
Circuit_Amplitude Modulation


  • Used to carry message signals in early telephone lines.
  • Can transmit Morse code using radio and other communication systems.
  • For Navy and Aviation for communications as AM signals can travel longer distances.
  • In amateur radio.


  • Because of amplitude modulation wavelength, AM signals can propagate longer distances.
  • For amplitude modulation, we use simple and low cost circuit; we don’t need any special equipment and complex circuits that are used in frequency modulation.
  • The Amplitude modulation receiver will be wider when compared to the FM receiver. Because, atmospheric propagation is good for amplitude modulated signals.
  • Bandwidths limit is also big advantage for Amplitude modulation, which doesn’t have in frequency modulation.
  • Transmitter and receiver are simple in Amplitude modulation. When we take a demodulation unit of AM receiver, it consists of RC filter and a diode which will demodulate the message signal or modulating signal from modulated AM signal, which is unlike in Frequency modulation.
  • Zero crossing in Amplitude modulation is equidistant.


  • Adding of noise for amplitude modulated signal will be more when compared to frequency modulated signals. Data loss is also more in amplitude modulation due to noise addition. Demodulators cannot reproduce the exact message signal or modulating signal due to noise.


  • More power is required during modulation because Amplitude modulated signal frequency should be double than modulating signal or message signal frequency. Due to this reason more power is required for amplitude modulation.


  • Sidebands are also transmitted during the transmission of carrier signal. More chances of getting different signal interfaces and adding of noise is more when compared to frequency modulation. Noise addition and signal interference are less for frequency modulation. That is why Amplitude modulation is not used for broadcasting songs or music.

Power Supply:

The project requires a regulated 5 volt supply voltage. The circuit shown in Figure converts an unregulated supply of 9 volts to 5 volts for use.


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