Simulating pierce crystal oscillator

Discussion in 'The Projects Forum' started by Faiz Valensi, Apr 21, 2016.

  1. Faiz Valensi

    Thread Starter New Member

    Jun 16, 2014
    7
    0
    Im simulating a pierce crystal oscillator on synopsys software. The design that i've made is to achieve 10MHz frequency. The problem is the circuit that ive made doesnt oscillate. Initial condition also been included before the inverter. Is there any error that I've made in this circuit? Thank you


    RF = 1M Ohm
    R1 = 1k Ohm
    C0 = 6p F
    Cstray = 5p F
    C1 = C2 = 22p F
    Pmos W/L = 6u/1u
    Nmos W/L = 3u/1u
     
  2. SLK001

    Well-Known Member

    Nov 29, 2011
    815
    225
    Have you ever had an oscillator work in your simulator before? I ask, because an oscillator is fairly difficult to get to start in a simulator. What I do, is place a CLOSING SWITCH that closes at T=0.1 seconds in the base of the active element. Sometimes it works, sometimes it doesn't. Sometimes, changing the switch close time helps.

    Also, your circuit isn't easily readable.
     
  3. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    When you asked for help, but you attached a unreadable value, I'm not sure how our helper how to help you?

    Please reattach a clear circuit.
     
  4. Faiz Valensi

    Thread Starter New Member

    Jun 16, 2014
    7
    0
    Sorry about that.. I will attach it back later, since the file is at another pc that has synopsys..
     
  5. Faiz Valensi

    Thread Starter New Member

    Jun 16, 2014
    7
    0
    Im working with ring oscillator and also VCO circuit. And it works pretty well, only the pierce crystal oscillator doesnt oscillate
     
  6. Faiz Valensi

    Thread Starter New Member

    Jun 16, 2014
    7
    0
    Sir, here is the reattach part. Sorry i have to seperate it since the component symbol is small.

    PierceForum_Faiz Valensi.gif
     
  7. eetech00

    Active Member

    Jun 8, 2013
    649
    112
    Hi

    Where are you setting initial conditions? I don't see the setting(s) anywhere.
    Try setting one side of the inverter (try output side) to 0 volts.
     
  8. Faiz Valensi

    Thread Starter New Member

    Jun 16, 2014
    7
    0
    Hello there.

    I already set the initial condition at the input side (to 0 volt).
    By the way is there any difference if i set the initial condition at the output side?
     
  9. eetech00

    Active Member

    Jun 8, 2013
    649
    112
    I would follow the rise of the power supply voltage.
    Which side of the inverter reaches steady state first based on power up?
    Are you able to set the ramp up time of all power sources?
    Try setting the power supply voltage source rise time to 25uS.
    Are you using the .UIC directive?

    I mainly use LTspice and this is usually solved by ramping the power supply or
    setting the initial conditions of specific nodes or devices (like caps).
     
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