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THS4131: much larger quiescent current over two general purpose op-amp?

Hisui Yan
Prodigy 180 points
Part Number: THS4131
Other Parts Discussed in Thread: THS4561, THS4531A

Dear Mr./Ms. TI,

    Could you clarify why the quiescent current of fully-differential amplifier is much larger than two general-purpose op-amp?

    For example, the Icc(Q) of the THS4131 is 16 mA under plus/minus 5 V, while the sum of Icc(Q) of two general-purpose (GP) amp may just 2 mA.

    So, if I use two GP amps to make a single-end to differential signal conversion circuit, will the power dissipation of the GP amp pair be similar with that of a fully-differential amplifier?

Thanks,

Qichen

  • 0
    Guru 48395 points

    The power budget for any device is a combination of many things - for the THS4131, a low noise target required more input stage current. Also, since it can operate on +/-15V and provide very large swings more power is required to give it some slew rate - unfortunately for these higher voltage parts, their quiescent does not change much going to low supplies, 

    We used to do a lot of app circuits to emulate an FDA before they were available, but the FDA does a nice job on setting the output CM voltage separately from signal path issues.

  • 0 in reply to Michael Steffes
    Guru 48395 points

    incidentally, if you need an FDA function on lower supplies, look at the THS4561 or THS4531A to save power, their noise is higher.