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3dB Bandwidth of THS4531

Julian Schneider1
Prodigy 20 points
Other Parts Discussed in Thread: THS4531

Hi,

I'm working on a balun for bandpass applications.

I have chosen the THS4531 for a conversion of a single-ended signal to a differential signal. The datasheet promises a 3dB bandwidth of 36 MHz at a gain of 1. I simulated the given test circuit with TINA and the TI-TINA model (figure 68 in datasheet). The result of the gain is shown below (orange line). In the simulation the THS4531 reaches a bandwidth of 30 MHz. As a second step I have built the schematic on a pcb. The measured gain (blue line) has a bandwidth of approx. 13.8 dB. For my application I need a bandwidth of 22.5 MHz. Now, my questions are as follows:

  1. Is it reasonable that even the simulation does not reach the promised 36 dB?
  2. How can the difference between simulated and measured results be explained?
  3. Is Texas Instruments able to build a pcb that fulfills the requirements?
  4. The simulation works up to a single supply voltage of 3 volts. At higher voltages the simulation collapses. Why? Is this effect based on the TINA model provided by TI?
Thanks in advance
Julian

  • 0
    TI__Genius 13935 points

    Hello Julian,

     I tried to duplicate your results in TINA and was unable to.  I get about 30MHz bandwidth using the circuit shown.  

    I started out with the reference design that is posted on the website and then modified it to match your circuit. 

     6675.THS4531_ref_2.TSC

    Can you try this schematic and see if it shows the same problem?  Were you using this same schematic on the measured results?

     

    Regards,

    Loren

     

  • 0 in reply to Loren Siebert 1
    Prodigy 20 points

    Hi Loren,

    thank you for your reply.

    Using the TINA reference design (from website) solved point 4. It's now possible to simulate higher supply voltages.

    But I still get just 30 MHz of bandwidth in simulation.

    The measured graph was recorded with the same schematic used in your reference design. It shows a bandwidth of about 14 dB. I'm not able to figure out why?

    Regards

    Julian