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THS4222 gain performance.

Other Parts Discussed in Thread: THS4222, OPA2690, OPA2691

Hi TI technical Support,

Please find the figure below.

Here i am confusing with first parameter.

In small signal bandwidth: test conditions it is showing that G=1,Pin = -7dBm. what is this mean exactly?

Is this gain tested with respect to input power.What is this parameter exactly mean"G=1,Pin = -7dBm".

Here my input parameters to OPAMP:

signal - Square wave , 4V peak-peak

1pF only can drive to OPAMP.

Frequency: 40MHz - 100MHz

-3db cuf off frequency - 200MHz.

I want to operate this op amp as unity gain buffer.

Thank You in advance.

Regards

Swapna.B

  • Swapna,

    dBm stands for decibels (dB) referenced to one milliwatt (mW). It is a common unit of measure in high speed applications.

    You can convert to Vpp with the following formula.

     

    Assuming the power is being delivered to a 50Ω system, you can calculate the peak to peak value of -7dBm below.

    This is the voltage seen at the input of the amplifier. So in a gain of 1V/V, 282mVpp will be seen at the output.

    Additionally, I've attached a spreadsheet to help with the calculation below.

    1588.dBm to Vpp conversion.xlsx 

    As far as the speed is concerned, the THS4222 may not be fast enough to drive 4Vpp at 200MHz. You can see that the full power bandwidth is limited to 65MHz at a gain of 1.

    Maybe you want to take a look at a faster device like the OPA2690 or maybe some current feedback amplifiers (OPA2691), which tend to have very good distortion and speed.

    Regards,
    Luke Lapointe
    High Speed Amplifiers