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Distribution Amplifier, or DA, is used to divide a single video source or audio source and duplicate it into two or more identical copies of the original signal. DA is available for both analog and digital audio and video signal types. Analog distribution amplifiers provide signal amplification and enhancement features such as fixed or variable peaking and gain. Digital distribution amplifier provide appropriate signal buffering so that each of the outputs may be driven without affecting the data path integrity and bit error rate performance. In some cases, digital DA will also reclock the signal at the output, ensuring that each of the output signals is at a data rate identical to the original signal.
Why is a Distribution Amplifier needed?
Whether the application is analog or digital, video and audio signals originate from the source with limited signal drive capability. Most signal sources are designed to support only one destination device, such as a monitor or projector. With analog video signals, for example, a source such as a Camera has signal output impedance of 75 ohms. The camera delivers maximum power to only one device, or load, the input of which is also matched at 75 ohms. Connecting a second 75 ohm load to a video source will result in only one-half of the original signal power being supplied to each load.
In addition to the primary effects of signal loading, the electrical characteristics of the cable, or transmission line, may come into play, which will affect the integrity of the original signal's electrical characteristics. In analog systems, the rise and fall times of the leading and trailing edges may become distorted or degraded, affecting the high frequency portion of the signal, which carries video and sharpness or detail information. For digital systems, signal reflection in the cable may cause distorted signal transitions that are misinterpreted by the receiver as data. This can result in the loss of synchronization with the source or cause the display of erroneous information.
How are they used?
Distribution amplifiers are essential for applications that require the simultaneous use of a single signal source with multiple projectors, monitors, DVDs, videoconference systems, or other destination devices. With computer-video signals, a high resolution distribution amplifier is commonly used to replicate and amplify the output of the computer's VGA port so that the signal may be viewed on two or more monitors at the same time.
One of the key features of distribution amplifiers is that two or more can often be cascaded to provide additional buffered outputs where one output of the first DA is connected to an input on the second DA. Often, the DA will include a dedicated output, typically an unbuffered pass-through of the input, for this purpose.
Choosing a Distribution Amplifier
Distribution amplifiers are essential for applications that require the simultaneous use of a single signal source with multiple projectors, monitors, VCRs, videoconference systems, or other destination devices. With computer-video signals, a high resolution distribution amplifier is commonly used to replicate and amplify the output of the computer's VGA port so that the signal may be viewed on two or more monitors at the same time.
To select the right Distribution Amplifier for a specific application, begin by identifying the key requirements necessary to support the design. For example:
- What signal format will be distributed?
- How many outputs are required?
- How far is the signal being run?
- How does the DA need to be mounted?
- What are your space requirements?
Categories
When selecting a DA, first define your signal and system requirements. Then, pick the product category that best fits your needs.
Line Drivers
Line Drivers enable long distance connections between one source and one destination. Video signals normally lose amplitude and high frequency response on long coax cables. Line drivers provide a variable gain control which may be adjusted to boost the video signal level, thus compensating for the overall drop in signal voltage. The peaking, or sharpness, control introduces a high frequency equalization boost which compensates for the high frequency loss that occurs in longer cables.
Audio/Video Distribution Amplifiers
A/V Distribution Amplifiers are available in a variety of models for composite video, S-video, component video, and stereo audio.
VGA and RGBHV Distribution Amplifiers
VGA and RGBHV Distribution Amplifiers support the various types of 15 pin connector and five BNC connectors per input and output. RGBHV distribution amplifier can also be used to distribute composite video, S-video, analog component video.
DVI Distribution Amplifiers
DVI Distribution Amplifiers provide multiple outputs to support groups of DVI-equipped digital display monitors. The DVI, or Digital Visual Interface, is a digital interconnect standard used between computer graphics cards and newer digital monitors. The DVI utilizes Transition-Minimized Differential Signaling, or TMDS, technology. There are two types of DVI connectors: DVI-I, which includes digital and traditional analog VGA support; and, DVI-D, which provides only digital signal connection support.
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