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Open loop gain and open loop phase for an oscillator

Pictou

 Hello,

I'm designing an oscillator with a quartz (Pierce model). The circuit is basically an amplifier and the quartz. I would like to measure the open loop gain and phase however I'm not sure about the method.

 First method I tried is the following :

I disconnected the loop at the gate of the MOS amplifier inverter. Put a vac source and set the AC amplitude to 1V.I copied the schematic of  the amplifier and pasted it at the output of the crystal, this way the crystal will see the same load as if it was in closed-loop. Then I measure the gain at the output of the crystal using a HB analysis.

 

Second method is :

I used the middlebrook analysis, which is stb in cadence. However I'm skeptical about this method as stb is to check the stability of the system. And, as I'm using an oscillator, I'm not supposed to be stable. However I'm still measuring an open loop gain and phase with stb analysis.

 

My question is which method is correct? I really have no idea on how to answer that question, so I'm here.

 

Thank you.

Parents

  •  Hello again,

    I'm experiencing some troubles with the PSTB analysis. In the example it says that I need to run a PSS first, however my PSS does not converge (even with a 10mS extra time to stabilize). I was wondering if there was another way.

     

    Thank you

Reply

  •  Hello again,

    I'm experiencing some troubles with the PSTB analysis. In the example it says that I need to run a PSS first, however my PSS does not converge (even with a 10mS extra time to stabilize). I was wondering if there was another way.

     

    Thank you

Children
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