Selecting video op amps

  
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The first versions operated from ±15V supplies, featured bandwidths of 50 MHz, and delivered slew rates in the low hundreds of volts per microsecond. Today`s fastest amplifiers run on ±5V supplies with bandwidths of 1. 4 GHz and slew rates of 6000V/ µsec. There are hundreds of versions available, and, to add to the challenge, many applications require the
Selecting video op amps - schematic

lowest possible supply voltage. To simplify the design choices, it`s important to identify major parameters of interest. Start with the kind of signal the op amp is passing, the available supply voltages, and the power dissipation that an application allows or tolerates. Important intangibles include ease of use and tolerance to board layout. This article covers the signal requirements and then reviews available amplifier topologies. Table 1 suggests amplifiers for different signals. The op-amp industry adopted the composite-video format in monochrome form in the early 1940s and the color standard in 1953 ( Figure 1 ). White-level, color, and horizontal- and vertical-synchronous signals combine onto one conductor. The synchronous signals originally guided the electron beam`s horizontal line-scan in early CRTs. In today`s digital televisions they perform memory-mapped data-stream timing. In US composite video, the synchronous pulses repeat at a 15, 734-Hz rate. A flat region that represents a dark display and includes a chroma burst follows each horizontal synchronization. The burst is a number of 3. 58-MHz sine waves that serves as a frequency reference for subsequent embedded color information. The composite-video receiver has its own chroma reference oscillator that resynchronizes each burst. The video-line-picture content follows the chroma burst. Figure 1 shows a sample video content in which a steady color amplitude...



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