Dealing with tradeoffs in coupling, clamping, and video filters

Video-filter drivers are necessary components to produce high-quality video equipment such as DVD, Blu Ray, set top boxes, and television systems. Even mobile equipment such as PMPs and cell phones need video-filter drivers to ensure the integrity of their video outputs as video goes mobile. To use a video-filter driver, a designer should be cognizant of the key interfacing methods and details such as clamp and bias, DC-restore, AC and DC-coupling of inputs and outputs, and other items. Video filter drivers typically employ either sync strip with pulse DC-restore or continuous time clamp/bias techniques.

Part of the evolution of these filters includes the adaptation of input- and output-interfacing methods to create simpler and more cost effective systems. The integrated circuit (IC) video-filter products that lead the market today have set new performance and cost standards. As video filter products evolved, so have their input and output coupling and clamping methodologies. This article looks at the some of the trade-offs of the different implementations of input and output coupling and input clamping methods that apply to video filters and identify their relative advantages and disadvantages.

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About the authors
The authors are with Fairchild Semiconductor Corp, as follows:

Earl Schreyer is a Member Technical Staff, with 19 years of experience in designing integrated circuits. He began his career with Fairchild Semiconductor in 1999 in the analog and mixed signal group, building on the analog and high-speed ADC work in the application of video/graphics digitizers and continuous-time video filter drivers.

Duane Sorlie is a Senior Staff Engineer for the signal-conditioning product line, with thirty-three years of experience in the semiconductor field He has written several articles and applications notes related to the system level implementation of “Video/Filter Drivers”.

Bill Boldt is a Senior Product Marketing Manager for signal-conditioning products, focusing on video, microphone, and amplifier products. Previously Bill held various marketing and general management positions with TDK Semiconductor, CP Clare (IXYS) and Silicon Systems, Inc., and also ran an industrial design firm.

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