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THS4022: THS4022 High speed op-amp amplification issue

Lakshmanan V
Intellectual 480 points
Part Number: THS4022


VGA_SPLITTER SCHEMATIC .pdfVGA SPLITTER_TOP PLACEMENT.pdfVGA SPLITTER_BOTTOM PLACEMENT.pdf

Hello sir

              We are using THS4022ID Op-amp in of my project. Here we are splitting one VGA input to Two VGA outputs ( Using THS4022ID ).

In RED colour input signal swing is upto 384mV. But my output signal just level shift to 1.6Volt, but there is no signal swing in my output side.

Hence my out on display monitor is just blank.

I request you to help me to debug further for solving the above issue.

Hereby attaching my input, output wave form and also my schematic,layout .

Thanks & Regards

Lakshmanan V

  • 0
    Guru 140200 points
    Hi Lakshmanan,

    the THS4022 needs a minimum gain of 10 to work stable...

    Kai
  • 0
    TI__Mastermind 23226 points
    Hi Lakshmanan V,

    Kai is correct, and you are only using a Gain=2. If you look at this amplifier's Aol, or open loop gain, which is the blue line in Figure 5 of the datasheet, you will see that the slope changes from -20dB/decade to -40dB/decade at around 20dB, or a gain of 10V/V. This type of amplifier is called decompensated, or non-unity-gain-stable. You can either Increase R40, R37, etc. to at least 4.5k and the amplifier will start working in a gain of 10V/V, or use a different amplifier that is unity gain stable.

    Best regards,

    Sean