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Similar part to OPA2846

Antony Lin
Genius 13480 points
Other Parts Discussed in Thread: OPA2846, OPA355, LMH6611, LMH6720, OPA690, OPA2836, TINA-TI

Hi,

Do we have similar part to OPA2846 but with an enable pin?  I can't find it in the database.

Thanks!

Antony

  • 0
    TI__Genius 13935 points
    Hello Antony,

    I am not sure what you key specifications are, but I found the following parts:
    OPA355
    LMH6611
    LMH6720
    OPA690

    Regards,
    Loren
  • 0 in reply to Loren Siebert 1
    TI__Genius 13480 points

    Hi Loren,

    THanks for the support.  Customer would temporarily be focused on OPA2836 at this moment. 

    Can you help to review the schematics as below?

    Thanks!

    Antony

  • 0 in reply to Antony Lin
    TI__Genius 13935 points
    Hi Antony,



    I would suggest simulating this in TINA-TI to see what the frequency response will be like.

    I am wondering what R52 would be used for?

    Also, there is normally a termination resistor between the amplifier output pins (low impedance) and the filter input. These could be added between the amplifier output pins and C109 and C108. In addition to providing termination for the filter the resistors would prevent C51 from causing instability with the amplifier outputs. Most high speed amplifiers do not respond well to capacitive loads on the outputs.

    Regards,
    Loren
  • 0 in reply to Loren Siebert 1
    TI__Genius 13480 points

    Hi Loren,

    Thanks fr your reply.

    As shown below, the input impedance is 380ohm.  Does customer still need to add 190ohm before C109/C108 for impedance matching?

    Thanks!

    Antony

  • 0 in reply to Antony Lin
    TI__Genius 13935 points
    Hi Antony,

    Unless the filter was specifically designed to have no termination, I would recommend the customer use the 190 Ohm resistors to properly terminate the filter.

    I would also recommend that the customer download our free TINA-TI software and simulate the circuit.

    Also, C51, C54 and C57 are fairly small (single digit pF). I would recommend that the customer try to estimate the PCB parasitic capacitances and include those in the simulation. It is common for a filter to have a frequency response that is about 10% lower than calculated when it is fabricated. One thing that helps mitigate this is to remove the ground and power planes directly underneath the filter components.

    Regards,
    Loren