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LMH5401: Related to stability @ unity Gain

shivakant dwivedi
Intellectual 960 points
Part Number: LMH5401
Other Parts Discussed in Thread: TINA-TI, THS4551

Hi Team,

I want to know that LMH5401 is stable for unity gain?.I am using this for single  to differential conversion.

Can i operate this for dual supply ie +2.5V & -2.5 V?

my signal frequency is 15 Mhz & Vpp=2V . Signal will be square or pulse .

I am using Vocm=0V

  • 0
    Guru 140200 points

    Hi Shivakant,

    no, the LMH5401 is not unity gain stable. Please read the datasheet (section 7.1, table 2, figure 56, etc.)

    Yes, you can operate the LMH5401 with +/-2.5V supply voltage.

    I would recommend to run the LMH5401 TINA Reference Design (Rev. B)

    TINA-TI is a free simulation tool and can be downloaded here:

    http://www.ti.com/tool/TINA-TI

    Kai

  • 0
    Guru 48395 points

    Why would you use an 8GHz part for a 15Mhz signal? 

    you should perhaps use the THS4551. 

    Recall, unity gain single to diff in an FDA is a noise gain of 2. 

  • 0 in reply to Michael Steffes
    Intellectual 960 points

    hanks Michael,

    For your quick response.
    Actually I need Ts (settling time < 10 ps).
     My application is for CCD waveforms . Along with that we are making our design for generalization like CRO.
    For upto 100 MHz BW, i require < 70 uVrms noise just input to ADC..Means echa Opamp should be  ultra low noisy.
    First stage we have Buffer & after that we have single to diffrential converor( which can supportunity gain along with other gain like 2, 4 etc).
    As these type of signal frequency is max 15 MHz & Vpp=2 ( or may be 4)
    image.png
    Please suggest suitable components.
  • 0 in reply to shivakant dwivedi
    Guru 48395 points

    Sure, lets say you want 1% accuracy in 10psec - that is maybe 4 time constants, or 2.5psec implying a required amplifier bandwidth of 63GHz - good luck. 

  • 0 in reply to Michael Steffes
    Intellectual 960 points

    Sorry Michael,

    It is 10 ns instead of 10 ps.

    Ts=*10 ns

    Could you suggest some P/N?

    Although I simulated LMH5401 through Tina. with Gain=1(For Vin= 10 MHz Square wave & Sine wave, 1Vpp)

    & Getting proper response without  oscillation.Is something i am doing wrong?

    Schematic is as follow:

  • 0 in reply to shivakant dwivedi
    Guru 140200 points

    Hi Shivakant,

    why are you doing this, if the datasheet does not recommend this?

    Kai