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OPA659: OPA659 Quiescent current

Ryuuichi machida
Guru 12085 points
Part Number: OPA659
Other Parts Discussed in Thread: OPA653, OPA656

Hello,

I have one question about Iq of OPA659.

According to datasheet, Iq spec is defined 32mA(typ).

I think that this is a little high comparing other OPAMP which have similar BW spec.

So, can you confirm whether this is typo or not ?

Best Regards, 

  • 0
    Guru 140200 points

    Hi Ryuuichi,

    it's not unusual that a HF OPAmp providing ultra low distortion draws a somewhat higher supply current. This can result from the output stage running in class A mode rather than in class AB or even class B mode.

    Kai

  • 0 in reply to kai klaas69
    Guru 48395 points

    Actually guys, 

    Part of a family of JFET parts we developed (table 5) - this one is using the high transconductance input stage along with higher Iq to get the very high slew rate in a unity gain VFA. Nothing to do with the output stage which is topologically class AB and stays that way - The supply current is a tested spec so what you see in the datasheet is correct. If you don't need the slew rate, go to the OPA656. And actually, that table 5 in the data sheet should be updated to include the fixed gain version OPA653. 

    I reviewed different ways to get a high slew rate VFA in this article where a bipolar high transconductance input stage was shown - should have had this OPA659 in those tables. 

    https://www.planetanalog.com/author.asp?section_id=3404&doc_id=565007&

  • 0 in reply to Michael Steffes
    Guru 140200 points

    Hi Michael,

    should be added to the datasheet...

    I guess there are lots of custormers (including me) who wonder why the supply current of OPA659 is such high.

    Kai

  • 0 in reply to kai klaas69
    Guru 12085 points

    Hello All,

    Thank you for your reply.

    One of benefit of OPA659, this device has good DC spec even though this is HS OPAMP.

    However, I understood that it trades off these specs against supply current(including Iq).

    We expect you will develop a little bit low Iq with same above good specs.

    Best Regards,

     

  • 0 in reply to Ryuuichi machida
    Guru 48395 points

    Well yes Ryuuichi, the best DC spec in this family is the OPA656B where both the offset and offset drift are screened. Just doesn't have anywhere near the LSBW.