18 Important Amplifier Glossary Terms

Amplifier

An electronic device used to increase an electrical signal and output an enlarged reproduction of that signal without substantially altering the original signal. The device draws power from a source other than the input signal. The input and output signals may be voltage, current or both (power).

Broadband Amplifier

An amplifier that amplifies electrical signals across a broad band of frequencies, with little or no signal decay across that range of frequencies.

Current Amplifier

An amplifier used to increase signal current, as opposed to increasing signal voltage or power.

Distribution Amplifier

A device that accepts a single input signal and provides this same signal to multiple isolated outputs. In audio-visual systems, an RF power amplifier used to feed television or radio signals to a number of different receivers, as in an apartment house or a hotel.

Dual Amplifier

A dual amplifier allows two (or more) channels of measurement or control to be housed in a single enclosure.

Frequency Response

The measure of a system's output to an input signal of varying frequency (but constant amplitude). Typically characterized by the magnitude of the system's response, measured in dB (decibels).

Gain

The amount of amplification achieved by an amplifier circuit. For example, a gain of 2 would mean the output is scaled to twice the amplitude of the input. In most references, gain is expressed as a decibel value (for example, 6 dB of gain).

Gain Range

The maximum and minimum voltage that can be used to amplify a signal.

Harmonic Distortion

The presence of frequencies in the output of a device that are not present in the input signal. The additional frequencies are multiples of components of the input signal.

Noise Figure

Noise figure is a comparison between the output signal to noise ratio and the thermal noise of the input signal. Usually measured as the difference, in decibels (dB), between the noise output of the actual receiver to the noise output of an “ideal” receiver with the same overall gain and bandwidth. A number by which the performance of a radio receiver can be specified.

Output P1dB/P3dB Compression

A measure of amplifier output power. Output power is defined in terms of the 1 dB compression point (P1dB) and P3dB (peak output power), which is usually very close to the saturated output power capability of the amplifier. P1dB is the peak output power at which the original input signal is compressed 1dB. P3dB is the peak output power at which the original input signal is compressed 3dB.

Power Amplifier

An amplifier used to drive significant power levels. Often used to provide power to other electronic components, or to strengthen signals from a preamplifier.

Preamplifier

An electronic amplifier that prepares a small electrical signal for further amplification or processing.

Rated Power Output

The maximum power available from an amplifier if normal specified operating conditions are observed. For example, an amplifier rated at 100 watts can produce output between zero and this maximum value.

Spurious

Noise or interference in a circuit, with qualities similar to the signal being transmitted or amplified.

Third Order Intercept Point

A measure that indicates how well a receiver performs in the presence of strong nearby signals. The intercept point is a purely mathematical concept, and does not correspond to any practically occurring physical power level. In many cases, it lies beyond the damage threshold of the device.

Travelling Wave Tube (TWT) Amplifier

A high-power amplifier of microwave energy. It accomplishes this through the interaction of an electron beam and an RF circuit known as a "slow wave" structure.