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Comparator Output Types

Hello Everyone

Can someone please direct me towards any kind of a literature which describe open drain, Open collector, Push Pull output types of comparators and what are the things we should consider when interfacing comparators with other Logic products like Flip-Flops. Thank you 

With best Regards,

Thilesh de Silva

  • Thilesh
    I will search our database of material and get back to you tomorrow. In the meantime, the best source of information in any comparator datasheet is the output voltage versus sink current and output voltage versus source current in order to determine compatibility with input logic. You will also find VOH and VOL specifications which specify output high and low logic levels for specific output current conditions which represent individual points on the curves previously mentioned. Sink current applies to both push-pull and open-drain output stages. Source current plots are specific for push-pull output stages only. In open-drain devices, the pull-up resistor value determines the output source capability.
    Chuck
  • In reply to Chuck Sins:

    Hello Chuck

    Thank you for replying me. Looking forward to hear from you..

    With Best Regards
    Thilesh De Silva
  • In reply to Chuck Sins:

    Hello Thelish,

    Comparator output types are covered in the TI Precision Labs Training series on Op Amps, specifically section 14:

    training.ti.com/ti-precision-labs-op-amps-comparator-applications-1

    The PDF of the course also contains the text:

    training.ti.com/.../2101 - Comparator Applications 1.pdf

    See PDF pages 9-11 (slides 6 and 7) for the output section.

    In short, a "Push-Pull" output has what you would think of a normal digital output. It connects the output to GND for a "low", and to V+ for a "high".

    A "Open collector" (or "Open Drain" for CMOS devices) only can pull low (to GND), like a switch. A pull-up resistor to V+ is required to go high (when the output is "open"). This configuration allows multiple outputs to be able to pull the same digital line "low" without conflicting (as in an FAULT line shared by multiple modules). So any of the comparators can pull the line low.

    Regards,

    Paul Grohe

    Low Power Amplifiers and Comparators (LPAC) Applications

  • In reply to Paul Grohe:

    Hello Paul

    Thank you for replying me and valuable information provided to enhance my knowledge in Operational amplifier and Comparators. I will go through the resources for further information. Thank you very much again

    with best regards
    Thilesh De Silva

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