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What is a Logarithmic Amplifier?

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  • Written By: Alexis W.
  • Edited By: Heather Bailey
  • Last Modified Date: 10 September 2016
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A logarithmic amplifier is used to identify any shifts in the input signal of a circuit and correct them. The logarithmic amplifier corrects the shifts through the conversion of the log input to a constant output voltage. Also referred to as a log amplifier, these types of electrical components have been used for years in electrical circuitry for the compression of input signals, as well as for maintaining a steady signal in signal computing.

Today, logarithmic amplifiers are often utilized in measurement or testing devices. “Log amps,” as a logarithmic amplifier is often called by the technical operators familiar with them, also have many uses in medical devices and video circuitry applications. Finally, they are often used as well as in fiber optics and wireless devices.

The fiber-optic cable and electronics industries began utilizing log amps in the 1990s to measure and maintain the signal intensity throughout the optical circuit after technology had advanced to the point where using these formerly bulky and expensive devices had become technologically and economically efficient. Prior to the 1990s, log amps were expensive because they were typically difficult to produce. The advancements in technology, however, allowed for a much more efficient production, decreasing the size and thus making them more easily applied. There are now three different types of logarithmic amplifier products.

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The first and most simple form is referred to as the DC log amp. DC log amps are strictly unipolar circuits, meaning they either maintain the current or the voltage of an input signal, but never both. Typically, these types of log amps are utilized within systems that are fiber-based as means of measuring the signal intensity within the system. They are not exclusive to fiber circuitry, however. DC log amps are also used in devices in the medical and biological research fields, mostly in units designed to process both biological and chemical sample pieces.

The other two log amps are referred to as baseband and demodulating, and each have their own specific frame of usage. Baseband, for example, is often used to compress the quickly changing signals used to power many AC-powered video or audio processing devices, at the same time compressing them to make them constant. Demodulating log amps, on the other hand, are used more in signal transmitting devices as a means of measuring the output signal being provided to the transmitter unit.

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