There are two major types of PAMs:

• Single polarity PAM: Here, an appropriate fixed DC bias is integrated with the signal to assure that all pulses are positive.
• Double polarity PAM: Here, the pulses are both negative and positive.

In some PAMs:

• The amplitude of every pulse is directly proportional to instantaneous modulating amplitude when the pulse occurs.
• While in other PAM, the amplitude of every pulse is inversely proportional to instantaneous modulating amplitude when at the occurrence of a pulse.
• In some other systems, the intensity of every pulse is based on particular characteristics of modulating signal other than strength like instantaneous phase or frequency.

Advantages of Pulse Amplitude Modulation

• PAM allows data to be transmitted more effectively, efficiently and quickly using conventional copper wires in greater volume.
• The frequency modulations available are infinite; hence PAM formulas can be developed continually to allow increased data throughput over existing networks.
• PAM is also the simplest form of modulation.