A video amplifier is device or module that amplifies, buffers and filters analog video signals to maintain signal fidelity across 75W cabling. Typical applications include video cable extension, video recording systems, floppy disk head amplifiers, pulsed amplifiers in communications products and any circuit that requires high-performance, low-noise signal gain.

 

Video signals can be presented to a video amplifier in different bandwidths for various video interface standards. These can include SDTV, composite (CVBS), S-Video, EDTV, VGA, SXGA/UXGA and HDTV variants. A video amplifier supports these standards by integrating selectable gain and filter characteristics for the circuit and the video standard. Filtering is needed for antialiasing video signals as they are typically generated by digital-analog converters (DAC) and received by analog-digital converters (ADC). Some amplifiers incorporate serial control protocols to enable amplifier adjustments through a processor or embedded system.

 

A video amplifier must have a quickstep response and signal overshoot characteristics to successfully amplify video signals to have high-quality image reception.   A video amplifier typically has a bandwidth range from 2-100MHz, and very large open-loop gain. To preserve the time domain shape of the signal, video amplifiers have a fairly flat frequency response (in the range of a couple of dB variation) across a wide frequency pass-band with low phase distortion. Several stages of video amplification may be incorporated.  Many video amplifiers are current feedback amplifiers (CFB) – the inverting input of the amplifier being sensitive to current changes instead of voltage. CFBs have no dominant filtering pole capacitor and, as a result, can operate much closer to the maximum frequency with higher effective gain.

 

Video amplifiers are optimized to have high bandwidth, low noise and are ideally suited to drive low impedance loads. Single packaged devices are available for single, dual and quad amplifiers.  Many video amplifiers can operate over a wide voltage supply range (for example +/-2V to +/-14V).  Some video amplifiers may consume less than 100mW of power configured in a split voltage supply arrangement.