3 Replies Latest reply: Nov 1, 2012 3:52 AM by michaelkellett RSS

Re: Common mode voltage range of comparator

chaitanya2k6er Level 2

I require a rail to rail comparator with common mode voltage range Vcc+1V, low power and high speed comparator. Suggest me some comparators that meets the requirement. Happy to recieve any kind of suggestions.

  • 1. Re: Common mode voltage range of comparator
    michaelkellett Level 15

    First you must define high speed and low power, and while you at it, Vcc (in volts).

    Then suggestions become possible.

    It might be better to explain what you are trying to do - there are few (if any) comparators that can cope with common mode voltages outside the rails and still be considered to be high speed. You may need to consider some novel ways to get round your problem.

     

    Michael Kellett

  • 2. Re: Common mode voltage range of comparator
    chaitanya2k6er Level 2

    Vcc can be any range more than 1V and device should be input & output rail to rail comparator. Acutually i need a comparator that works with single supply where the input signal varies from -1V to +0.7V. So i have planned to bias opamp with negative rail and ground the positive supply. So inorder to satisfy the condition i require a comparator that withstand +1V above the VCC. I have googled some comparators but i could not find any comparator with common mode voltage range more than 200mV. So suggest me some comparators that meets the requirment.

  • 3. Re: Common mode voltage range of comparator
    michaelkellett Level 15

    You still haven't said how fast !

     

    But, if you are using an op amp as a comparator you are not going to be very fast (and if you care about power check the supply current drain of the op-amp if you bias the inputs close to the or outside the rails.

     

    Use an inverting amplifer with a gain of 1 and a reference voltage of 1V to level shift the input signal, then use  a real comparator on the output of the op amp.

     

     

    Michael Kellett