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What Is the Difference Between a Modulator & an Amplifier?

Amplifiers and modulators are different, though related, electronic circuits, used for radio, audio and other kinds of signals. Of the two, the modulator is more complex; it encodes one signal into another signal of greater frequency to efficiently transmit information. An amplifier is a simpler device, increasing the strength of the signal passing through it.

Inputs
- A modulator has separate inputs for two signals, called a carrier and a modulator. Radio modulator circuits, for example, have a modulator signal consisting of audio, such as music and speech. The carrier signal is a sine wave with a fixed frequency between 540 kHz and 108.1 MHz. The carrier̵7;s high frequency ̶0;carries̶1; the audio signal with high fidelity. An amplifier has one signal input. Different kinds of amplifiers handle audio or radio signals, outputs from scientific equipment or other kinds of electronic sources.
Gain Control
- Amplifiers typically have manual gain controls, used to vary the strength of the output signal from zero to a specified maximum. The gain control may be a rotary knob, linear slider or pair of digital up/down buttons. Modulators also have gain controls, though used for different purposes. A technician adjusts these occasionally to obtain an optimal level of modulation. If the carrier or modulator signal is too strong, the output signal distorts.
Types
- Amplifier circuits come in several designs, called classes. A Class A amplifier, for example, has a simple design, consisting of a single vacuum tube or transistor. It has the best fidelity of any amplifier class, though it has poor operating efficiency. Class AB, B, C and D amplifiers have progressively better efficiency and worse fidelity. Modulators also have types based on the kind of modulation they perform. An amplitude modulator, AM, for example, controls the height of the carrier wave signal with the modulator signal. A frequency modulator, FM, increases and decreases the frequency of a carrier signal slightly, using the modulator signal. Phase modulation alters the phase angle of the carrier, and digital modulation shifts a carrier̵7;s frequency in discrete amounts to carry digital computer data.
Use
- Amplifiers have many consumer, commercial, industrial and scientific applications. A mobile phone, for example, has a radio amplifier to boost the signal coming from a local cell tower. It also has an audio amplifier to drive the earpiece speaker. Musical instrument amplifiers drive large speakers to fill a room with sound. A car audio system may have several amplifiers used to power different kinds of speakers. You find modulators in radio transmitters, portable telephones and computer network equipment.

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