BVD equivalent circuit of a quartz crystal

Discussion in 'The Projects Forum' started by rt123, Aug 14, 2009.

  1. rt123

    Thread Starter New Member

    Jul 30, 2009
    Hi all,

    I need to find the equivalent BVD model of a quartz crystal which is being fabricated by one of my labmates. All I have is the area of the electrode (dia. 50 um) and the thickness (10um) and I need to find the RLC values which can then be plugged into a Spice simulation of an oscillator circuit.

    Could someone please help me out with this!

    Thanks in advance.
  2. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    Indeed I can. From the ARRL Handbook:

    A crystal consists of a series resistance, capacitance, and inductance. A capacitor (holder capacitance) is in SHUNT with the three above series components.

    For a 1MHZ crystal:

    Series L=3.5 Henry
    Series C=.007 picofarads
    Series resistance=340 ohms
    Shunt capacitance=3 picofarads

    These values can be essentially scaled for any fundamental crystal in the H.F. range. Notice the HUGE L/C ratio of the series elements....this is where the Q comes from!