question about level shifter circuit

Discussion in 'The Projects Forum' started by namratha28, Apr 4, 2009.

  1. namratha28

    Thread Starter New Member

    Apr 4, 2009
    5
    0
    Hi
    I have been trying to build a circuit which works as a voltage level shifter. So the input voltage ranges from 2.5V to 4.5 V. I am supposed shift it down to 0 to 2.5 volts. I was thinking of using a comparator kind of circuit, but I am not sure of how to use it. It would be great if I could get to know what kind of circuit I should make use of.

    Thanks
    Namratha
     
  2. onlyvinod56

    Active Member

    Oct 14, 2008
    362
    1
    Hi namratha.
    check the attachment. it is a positive clamper.
    to convert it into a negative clamper, just revrese the diode terminals & dont forget to change the connections of 10K pot (non inverting '+') from +15v to -15v.
    i didnt check this. try it on a bread board.

    For what sake u need to shift the level. Can u forward ur scematic? If it is a precise one, u need to go for precision opamps.

    all the best.
     
  3. namratha28

    Thread Starter New Member

    Apr 4, 2009
    5
    0
    Hi
    Thanks a lot for taking time and sending me the circuit. I will try to test it using a bread board.
    In my university , we are building a car which will be used for a competition. So I am in the analog front end part of the team.
    The schematic hasn't been totally prepared yet, but yes, this level shifter will be going in between a rectifier and a RC filter. We are using a X-mega chip for the purpose. I will sending the part of the schematic which I would be working on.

    Thanks a lot once again for helping me.

    Thanks
    Namratha
     
  4. rajasekaran.raman

    New Member

    Apr 6, 2009
    3
    0
    Please kindly tell me, level shifter circuit is essential in diffrential amplifier because as there is no ____________ in the circuit,...

    and also please reply me what would be the answer for in Op amp Circuit,..
     
  5. namratha28

    Thread Starter New Member

    Apr 4, 2009
    5
    0
    Hi Rajasekaran Sir
    The reason level shifters are needed in diff amps is that the circuit which provides input to the diff-amp may not be differential, example if the input is 0V and 5V, then the level won't be centered around the virtual ground, hence there may be common mode amplifications ( if there is a noise in the signal then that would be amplified). Hence level shifters ensure that the input signal would be centered around the virtual ground (eg: -5V to 5V) to make the diff-amps behave the way they should.
    For op-amps, level shifters are required because the amplifiers inside an OpAmp are DC coupled (no AC coupling capacitors). Each amplifier stage produces AC amplification of the signal but at the same time the DC level is shifted due to the bias voltages. The output of each stage is supposed to have minimum DC shift.

    A level shifter placed in between gain stages shifts the DC level back to zero volts (or close to it as required by the design), so that the overall DC path is maintained (input to output).

    This means you can amplify a DC signal (at the input) and get the proper DC output.
    I hope this answers the question you asked Rajasekaran Sir.

    Thanks
    Namratha
     
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