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Op Amps with good Recovery Time characteristics

Martin Bishop
Prodigy 125 points
Other Parts Discussed in Thread: TL072, TLV9102, LMH6643, TL072H

Op Amp selection for a minimal component clipper / limiter is my interest

Recovery Time is the parametric most indicative of good performance; unfortunately its charachterisation is uncommon

Constraints firstly: 5V single-rail operation, VFB internal architecture, audio frequency range, dual in standard pinout.

Key requirement: release time after limiting/clipping at/below the rails, 1st stage will take an ~1Vpp LTC (linear time code, 2k, 4k8, ... Hz content) and diff Rx it with again of ~5, 2nd stage will slice it using a comparator topology.  A 3 rd party conceptual design shows the use of a TLC2271ID as working fiction.  In the past I have seen similar processing done with TL072's.

Attributes such as RRO and RRI may assist, but really it is the recovery from the rails of drive saturation that matters.


The output of interest is the timing of the zero crossings, their nominal minimum spacing is 1 / 4.8 kHz i.e. 208 us, so the release time requirement is modest < 1 us VG, < 10 us tollerable.  However, less jitter should enable the design of a more discriminating detector.

I am discounting the use of zenners and biased diodes in the feedback path, the classic precission clipper designs, too many parts for the BoM and you can't get zenners with a sufficiently low zenner voltage.

  • 0
    TI__Expert 6535 points

    Hey Martin, 

    With an emphasis on the overload recovery time, you've mentioned you want these specs included: 

    • 5V single-rail operation
    • Voltage Feedback internal architecture
    • audio frequency range 
    • dual in pinout

    To help narrow down your search, please include:

    • package type
    • output current
    • slew rate
    • supply current

    And could you confirm the unit of your gain? V/V? or dB? 

    I also noticed the TL072 meets the overload recovery requirement of less than 1us at 300ns. If your concern is the overshoot, I suggest reducing the gain in your application or increasing the supply voltage.

    Regards,

    Ore.

  • 0 in reply to Ore Ogundana
    Prodigy 125 points

    Hi Ore

    Thank you for getting back to me

    Responding to your specifics:

    - SOIC-8 [D0008A] Package : primarily for ease and availability

    - output cuttent negligible : one stage feeds the next thro ~47k, the second stage feeds a 74LVC1G17GW thro 10k

    - slew rate modest : the 1G17 has a Schmidt trigger input and is therefore tollerant to slow transitions (not that I expect that to be an issue), less than a volt / us is the ballpark (not obviously challenging)

    - supply current, anything within reason - I would expect a few mA quiescent, we are not on a tiny battery

    Diffl amp gain is 5 v/v, comparator gain is 20 v/v

    The TL072 was a side comment, it will not play on 5v rails, more an existence proof.

    The 5v single supply configuration is immutable, this is a small part of a larger design with limited regulated power 5v, & 3v3.

    Overshoot is not a concern, the high gains are intended to drive the signal into saturation / overshoot.  The only aspect of the signal of interst is the timing of the zero crossings.

    Parts I have considered include TLC2272AID, TLV9102, LMH6643 (discounted as CFA)

    I look forward to your response

    Martin

  • 0 in reply to Martin Bishop
    Prodigy 125 points

    Hi Ore

    Further to my last, having rummaged more, I note that the TL072H is a candidate : recovery time (as you observe) good enough, no phase reversal, 100 mV from rails with 10 k load and OK for 5V single supply operation.

    Is there a method for preparing a shortlist from your public parametric tables - which seem to lack the necessary params

    Martin

  • 0 in reply to Martin Bishop
    TI__Expert 6535 points

    Hey Martin, 

    Asides from using the filters on the general purpose amps page on our website: https://www.ti.com/amplifier-circuit/op-amps/general-purpose/products.html, TI has also provided the Op-amp Selguide software that allows you to select Op-amps with specific parameters for your application. You can download the software here: https://www.ti.com/tool/OPAMPS-SELGUIDE.

    Once you have the software installed, click "Search" in the top left corner and use the filters to narrow down your search. 

    Using the software on my end, I was able to find these op amps that matched your specs: 

    Turns out the OPA192ID has a faster overload recovery time than the TL072 (200ns vs 300ns respectively)

    Feel free to use the software to be as specific as you want. 

    Regards,

    Ore. 

  • 0 in reply to Ore Ogundana
    Prodigy 125 points

    Hi Ore

    I have scored your response as "did not solve my issue".  Why, neither the search program nor the online search capability provide parameters such as No Phase Reversal or recovery time to enable a parametric search.  Nonetheless thank you for taping the OPA192ID as another candidate.  Although for this application, I think either the TL08x or TL07x is more suitable.

    It would be a good thing if your parametrics were extended to premit searching on this sort of second order characteristic.  FWIW AD's search engine is similarly deficient

    Best Regards and Many Thanks

    Martin