Amplifying VGA Signals

Discussion in 'The Projects Forum' started by Dalaran, May 12, 2014.

  1. Dalaran

    Thread Starter Senior Member

    Dec 3, 2009

    I need to amplify 1V outputs from a VGA card up to ~4V - RGB as well as Hsync and Vsync.

    Is there any issues in using a standard op-amp IC configured as non-inverting op-amp for this? Also will a breadboard or perf-board be sufficient to handle the VGA frequencies?

  2. MrChips


    Oct 2, 2009
    Are you working with strictly 640x480 VGA or possibly higher resolutions?

    VSYNC is typically 60-100Hz
    HSYNC is typically 31.5kHz but can be higher for other standards.

    Your concern will be the Red, Green and Blue video signals which are 25MHz and greater.
    You will need a video amplifier for this.

    A breadboard or perf-board will result in poor performance at those video frequencies.
  3. DickCappels


    Aug 21, 2008
    Well, the unterminated output of a VGA card is 2 volts P-P, so you are halfway there already. If you are only driving a light load, you can get by with a simple transistor amplifier, or as MrChips says, use an integrated amplifier.

    You could start with this circuit and adjust the value of the emitter resistors (R6 in the first amplifier) and the base bias voltage.

    You can find an opamp with a gain-bandwidth product of 100 MHz or 150 MHz (might be able to get away with a little less, but I doubt it) and adequate slew rate capability.

    If you describe what your goal is in more detail, such as the characteristics of the load and whether it needs to be clamped to a particular DC level would help, we might be able to offer more specific help.
  4. Dalaran

    Thread Starter Senior Member

    Dec 3, 2009
    Thanks a lot for the replies.

    The application is a MAME arcade machine. I have built a few over the years but always put in an LCD monitor so I can connect directly through VGA/DVI to the PC. I am building one for my Dad, and he wants to keep the original arcade monitor. Manual found here: G07-904_Manual.pdf

    The video card I am connecting to is made specifically to convert standard PC monitor resolutions to Arcade monitor ones. It can be found here:

    The card outputs 1V signals that works with many monitors but not this one. The same guys sell a video amp board, but I figured this would be a neat little project to tackle.