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OPA365-Q1: Layout Qs to use it as comparator as well as an amplifier in a circuit

Part Number: OPA365-Q1
Other Parts Discussed in Thread: OPA365

A customer of ours is trying to use an OPA365-Q1 for double functionality (the schematic where all of this is reflected would have to be shared privately via PM or similar):

For one thing, they want to use it as a comparator; for another they need its output to be used as an amplifier for an integrating circuit. Because their implementation is not working and there’s deviation to simulated data, they've a couple of questions to this part:

  1. Can the OPA365-Q1 actually be used as a comparator with the following estimation: 4V/us < d(Uein+)/dt < 40V/us, while Uein- is constant (approximation).
  2. How big is the maximum offset from Uaus_1, if the latter should actually output 0V with respect to ground. Are there any functional dependencies to the circuit that follows at this output. If so, how can these dependencies be quantified?
  3. How big is the propagation delay for a rising or falling edge (pulse) to be reflected at the output?
  4. What happens, when the pulse width at the input (Uein+) is smaller than the propagation delay

Thanks and regards,
Simon

  • Hi,

    The OPA365 can be configured as a comparator, but it has a maximum slew rate of 25 V/us so the output response would be much slower than the 40 V/us input condition.

    I am not sure what you are referring to with the name "Uaus_1", can you please clarify.

    To look at propagation delay it will depend on the circuit configuration and will be determined by the phase response of the amplifier. Realistically different frequencies will be delayed depending on the exact phase shape of the amplifier's closed loop response.

    Regards,
  • Hi Jacob,


    I've sent you a PM with the Schematic so you can review and can come back with the answers.

    Thanks and best regards
    Simon
  • Hi,

    Looking at the schematic, the customer is going to need to use a faster device than the OPA365 to achieve the specs they are looking for. At 40 V/us, the OPA365 shows almost no output from the comparator stage.

    Regards,
  • Hi Jacob,

    What would be a faster part that would meet the requirements?
    And how does this new proposal fits that list of 4 questions.

    Thanks,

    Simon

  • Hi Simon,

    I would actually suggest using a dedicated device from our comparator portfolio. It will make the design simpler and they are optimized specifically for slewing.

    Regards,