• State
  • Locked Locked
  • Replies 6 replies
  • Subscribers 49 subscribers
  • Views 282 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

BUF634 in parallel: BW pin connection

BUF634A: Paralleling devices

Michal Tyc
Prodigy 180 points
Part Number: BUF634A
Other Parts Discussed in Thread: OPA2677, , OPA2670, BUF634

Tool/software:

Dear Support Team,

We consider paralleling a few (say, four) BUF634As to increase the output current. Is it advisable? We cannot find any notes in this topic. We have conducted simulations in TINA and the results look promising, but we are conscious that the models do not fully replicate the reality.

If it is fine, how small can be the current equalization resistors at the output of each device? We would like to avoid unnecessary heat dissipation.

Best regards,

Michal

  • 0
    Guru 48395 points

    you would be better to use the OPA2677 dual CFA line driver in a unity gain configuration, it can actually put out over 1A in each of the two devices of this dual. This is an early DSL line driver where it was not completely clear how much current we needed. So, the K.20 testing needed to absorb over 1.5A and this part did very well as it could do that (kind of by accident)

  • 0 in reply to Michael Steffes
    Guru 48395 points

    Of course, the 12V OPA2677 can't do as much voltage swing as the BUF634A,There are 30V DSL line drivers also that put out quite a lot of current as well, but no where near the OPA2677

  • 0 in reply to Michael Steffes
    Prodigy 180 points

    We have already considered OPA2670 which is similar to OPA2677 but we rejected it due to its capacitive load restrictions. The capacitive load can vary widely in our application and the series resistor value suggested in the datasheet is too big for the output current which we need. 

    Is the suggested series resistor value required for general amplifier stability? If the series resistance would be smaller, do we risk instability, or just some gain peaking?

  • 0 in reply to Michal Tyc
    Guru 48395 points

    Well Michal, can't go much further without the cap load range, desired speed and signal swing

  • 0 in reply to Michael Steffes
    Prodigy 180 points

    We need cap load range is from 100 pF to a 10 uF, frequencies up to 50 kHz for low capacitances and 10 kHz for high capacitances, amplitude +-3 V. Our simulated circuit with four BUF634As in parallel seems to meet such criteria, but we need to know if it safe to use it in this way.

  • 0 in reply to Michal Tyc
    TI__Genius 9730 points

    Hi Michal,

    Using a buffer in a parallel configuration can be implemented. One concern from the values you presented is the current required specifically in the 10uF condition. I will attach an article that highlights the use of parallel BUF634 devices and performance considerations that can be applicable to your application. 

    Combining_an_Amplifier_with_the_BUF634 (ti.com)

    Best Regards,

    Ignacio