Component Values for Colpitts Crystal Oscillator

Discussion in 'The Projects Forum' started by sailmike, Feb 28, 2015.

  1. sailmike

    Thread Starter Member

    Nov 11, 2013
    143
    3
    I need to pick component values for a colpitts crystal oscillator. Someone else picked the values for the oscillator shown in the attachment for a 12 MHz crystal. I want to use a 4 MHz crystal. I'm pretty sure C1, C5, R2, and R3 don't need to change. The values for Rm, Co, and CL come from the data sheet for the 4 MHz crystal. I'm not sure how to pick the values for the other components in the circuit.

    Thanks,
    Mike
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    If your decreasing the frequency by 3, then increase the capacitors by 3, so 47pf to 150pf.
     
  3. sailmike

    Thread Starter Member

    Nov 11, 2013
    143
    3
    What would the equations be for this circuit?
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
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