How to gain a VGA signal with op amps to use with logic IC's?

Discussion in 'The Projects Forum' started by Eskapist, Feb 27, 2016.

  1. Eskapist

    Thread Starter New Member

    Jan 4, 2012
    Hi AAC members. :D

    This is a longshot.

    I am making a project where I am trying to modify a VGA signal through some 5v IC’s, like the CD4017, 74HCT08, SN74HC595, etc.
    It is not going to be perfect and I expect some kind of glitch, which I think could be aesthetic.

    The VGA standard have three separated colorchannels R,G and B, which goes from 0v to 0.7v.

    Do you know if it possible to build an op amp to gain each signal from 0.7v to +5v?
    And of course get them back down to 0.7v in the end? ;)

    Will the frequency be a problem? And is there a way to limit the voltage to 0.7v in the end, so I can experiment without damaging my screen?

    Also if you guys have an idea to a schematic, that would be great! :D

    Sorry for all the questions. :)

  2. ian field

    AAC Fanatic!

    Oct 27, 2012
    Anything past the original VGA standard could have a dot clock in the hundreds of MHz. Standard op-amps and CMOS logic won't cut it.

    Elantec is one company I've heard of that does video amplifiers that vaguely resemble op-amps. If you want to use logic - it may have to be ECL, you might just about get away with F or S variants of the TTL families.
  3. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    Analog Devices, Elentec, Texas Instruments, Linear Technology, Maxim, and Intersil all make triple video opamps for VGA signal processing. Note that while the sync signals are digital logic signals compatible with 3.3 V and 5 V logic chips, the three video channels are analog signals. No matter what the signal amplitude is, you cannot run them through logic chips like a 4017, 08, or 595 without destroying the video information.

    What is it you are trying to build?

  4. Eskapist

    Thread Starter New Member

    Jan 4, 2012
    Thanks for the answer Ian. I will look into them. :)

    Oh, thats a lot of interesting chips, thanks!

    I am trying to make a video synthesizer with some effect modules. I am trying to make it experimental, so the weird "destroying" video information difficulty is not an issue. :)