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.
I must admit that it must be hard to help me while I give you vague answers.
I don't know how to use the customer support, as an intern I'm not even sure I can use it, I will ask my manager as soon as possible.
Meanwhile I'm focusing more on the negative resistance approach, do you know if I can find a tutorial for this approach using CADENCE?
From what I understood, I need to replace the quartz model by a current source. The voltage drop across the current source will give me an impedance, then I should be able to extract the negative resistance from the impedance I'm reading. Am I correct? (I still need to study this method to fully understand but I think it's the broad idea).
Thank you for your help.