Comparator equal to Op-Amp

Discussion in 'Homework Help' started by menewbie, Mar 8, 2006.

  1. menewbie

    Thread Starter Active Member

    Jan 31, 2006
    34
    0
    I know the Op-Amp can be used as a comparator, signifies the difference of the input voltages. I am wondering can a comparator be used as an operational amplifier? If so, how? I I think in order for a comparator to be used as an Op-Amp, the comparator itself would need to have a very high gain. But not so sure if that is right...
     
  2. Papabravo

    Expert

    Feb 24, 2006
    9,906
    1,723
    An opamp and a comparator both have high open loop gain and may differ in details like frequency response, common mode range, input bias currents and so forth.

    The really important distinction is that a comparator usually has an open collector digital (not analog) output. The output is usually pulled up to a logic supply which is different from the analog supply. This output is generally very uncomfortable in any state between the lower supply rail and the logic supply. An opamp can both source and sink current. An open collector output can only sink current.
     
  3. menewbie

    Thread Starter Active Member

    Jan 31, 2006
    34
    0
    Thank you for the reply...I can see why comparator cannot be used as an opamp. But can a comparator function as an inverting-amplifier circuit if the comparator is designed to produce analog output??
     
  4. Papabravo

    Expert

    Feb 24, 2006
    9,906
    1,723
    The answer is a qualified maybe. It is sometimes hard to answer hypothetical questions like this without direct experience. In my opinion the investment of time in researching this question has a most dubious payoff. This is something I would not even contemplate doing in an actual design.

    Let me know your answer if you decide to look into this.
     
  5. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    hello,

    its been quite a long time that i've visited the forum.

    if i might add, try to compare the internal circuit design of a comparator and an op-amp. i believe it will provide you the answer to your query. :D

    moz
     
  6. pebe

    AAC Fanatic!

    Oct 11, 2004
    628
    3
    Hi Moz.
    Welcome back!
     
  7. menewbie

    Thread Starter Active Member

    Jan 31, 2006
    34
    0
    I will spend some more time to investigate this problem...and I will keep your updated.
     
  8. menewbie

    Thread Starter Active Member

    Jan 31, 2006
    34
    0
    Thank you for the reply. I will look into the internal circuit design.
     
Loading...