How to create "DC offset voltage" in crystal oscillator ?

Discussion in 'Analog & Mixed-Signal Design' started by Ngô Đình Nhân, Oct 17, 2018.

  1. Ngô Đình Nhân

    Thread Starter Member

    Jan 8, 2017
    45
    0
    Hi all

    I am doing a Pierce Oscillator with a quartz crystal. But I don't know how I can create a DC offset at point (a) or (b) in that circuit ?

    Please see me attached image for more clear.

    So, does any give me some recommendation ? I really appreciate your helps.
     
  2. Picbuster

    Well-Known Member

    Dec 2, 2013
    933
    121
    add an opamp or transistor plus a negative supply

    Picbuster
     
  3. Ngô Đình Nhân

    Thread Starter Member

    Jan 8, 2017
    45
    0
    Hello Picbuster

    thanks for feedbacks

    Do you think your solution will affect to resonance frequency of circuit ?

    Best regards
    Ngo, Dinh Nhan
     
  4. Bordodynov

    Well-Known Member

    May 20, 2015
    2,281
    700
    Usually (when using a CMOS inverter) between the points a and b put a resistor. At frequencies of 32 kHz, this is 10 - 30 Mega ohms. And frequencies greater than 1 megahertz are approximately 100kΩ -1MgaOhm.
     
  5. Ngô Đình Nhân

    Thread Starter Member

    Jan 8, 2017
    45
    0
    Hello Bordodynov

    Thanks for reply.
    In a real circuit, I had areadt put a 2.2Meg Resistor between a and b.

    But my problem is that i need a DC offset at a or b as my draw in image.

    So, do you have any recommendations?
     
  6. Bordodynov

    Well-Known Member

    May 20, 2015
    2,281
    700
    What kind of inverter are you using? Detailed information increases the opportunity to help you. But I can say that the resistor stabilizes the DC operating point. At the input, a DC offset is supported equal to the inverter switching threshold.
    2018-10-17_14-28-42.png
     
  7. Danko

    Active Member

    Nov 22, 2017
    705
    292
    Use this circuit:
    offset.png
     
    Ngô Đình Nhân likes this.
  8. Bordodynov

    Well-Known Member

    May 20, 2015
    2,281
    700
    See
    2018-10-18_14-20-20.png
     
  9. Ngô Đình Nhân

    Thread Starter Member

    Jan 8, 2017
    45
    0
    Thank you so much, all

    I am going to test this circuit topology.

    Best regards, all
     
  10. Danko

    Active Member

    Nov 22, 2017
    705
    292
    Good luck!
     
  11. fernandopv

    New Member

    Oct 20, 2018
    10
    1
    Perhaps you need to add this: (it will work with senoids too after some cycles)
    [​IMG]
     
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