Latching Analog Subtractor?

Discussion in 'General Electronics Chat' started by signedconfused, Nov 15, 2009.

  1. signedconfused

    Thread Starter New Member

    Nov 15, 2009
    Hi folks, first time poster here. :)

    I'm trying to think of what I'm going to need for my project. The best I can think of would be a Latching Analog Subtractor. But really, what does that mean...

    I have a sensor that will output a voltage when first started, then it will perform and vary from 0-5V. What I need to do is take the voltage that is first applied and have the system subtact that value from the varying voltage. The thing is the startup voltage will always be different.

    An example would be...The system starts up and has 1.2V. Then after the start up it moves to 3.2V. I need to have the output be 3.2V-1.2V.

    That's one time, it could start up again and be the system to check the voltage everytime. Otherwise I'd just use a resistor :)

    Any ideas?

    Thanks folks!:D
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    Are you sure AC (capacitor) coupling won't work? This will get rid of any DC component.
  3. BillB3857

    AAC Fanatic!

    Feb 28, 2009
    An op amp sample/hold circuit followed by an op amp summing amp should do it. The trick will be to trigger the sample hold circuit at turn on.
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
    S&H will droop over time, unless A/D and D/A conversion are used.