THS7373/THS7374 - To AC-couple or not to AC-couple?

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    • THS7373/THS7374 - To AC-couple or not to AC-couple?

      Hi! I've found this article and I'm a bit confused about what's the best option: To AC couple or not to AC couple? That's the question!

      I'm doing some tests with different TV sets and games and it works with both AC coupled and DC coupled outputs. Is it really convenient or adequate to AC couple the video signal with modern ICs like THS7373? or it's better to DC couple in sake of signal integrity?

      Inputs are AC-coupled using 100nF capacitors to get rid of the DC offset.
    • What are you trying to achieve exactly, amping video output? If so, from which devices?

      I only recently purchased the Ultimarc video amp, which only seems to support DC coupled video outputs. Looking to build an AC coupled video amp circuit with the THS7375 to amplify the Naomi's video output.

      The post was edited 1 time, last by Sp33dFr34k ().

    • I'm using a THS7373 as video buffer for my supergun to connect arcade boards to SCART TV sets or maybe an OSSC.

      In Tim's AV Driver CSYNC is DC-coupled while RGB signals are AC-coupled... and now this article makes me consider if DC-couple all the signals is the best for this amp.

      I found another document that favors the idea of DC coupled output:

      Maxim Integrated wrote:

      Despite these complications, video signals must be AC-coupled at the point where the voltage domains change. Connecting two different power sources through a DC connection is dangerous, and usually forbidden by safety regulations. Consequently, video-equipment makers have a tacit agreement to AC-couple the input of their equipment, and DC-couple the output—requiring the next stage to re-establish the DC component (see EN 50049-1 for PAL/DVB [SCART] and SMPTE 253M section 9.5 for NTSC, which allow a DC output level). Failure to establish such a protocol leads to "double coupling," where two coupling capacitors appear in series, or to a short where there are no capacitors. The sole exception to this rule is battery-powered equipment, such as camcorders and still cameras, which AC-couple the output to minimize battery drain.
      Update: I've moved to DC-Coupled outputs. So far, so good, will update if I find any inconvenience. :thumbup:

      The post was edited 2 times, last by rsignal ().