Hello Logan,

So my oscillator model is here :
http://www.pdfhost.net/index.php?Action=Download&File=3b8d65b711906580170bda9676...

C1 will include input capacitance of the amplifier.
C2 will include output capacitance of the amplifier.
Rin will be assumed to be infinite or at least really high
Rout is around 83Ohm but it may change. My transconductance is 12mS, so the Rout must be around 83 Ohm to have a gain equals to 1.

To determine the drive level of the crystal I'm going to do the following :
- To simplify the problem I will assume that the voltage exciting the crystal is perfectly sinusoidal (I know it's not really the case, in my simulation I have a component in the 2nd and 3rd harmonic at about 5% of my fundamental)
- I will calculate the impedance of the crystal depending on the pulsation w, the relation can be found here, in the electrical model tab :
http://en.wikipedia.org/wiki/Crystal_oscillator

I will simulate the circuit to find the oscillation frequency.
From this I will compute P = V²/Z(f).

Is this method correct?

Thank you for your help.

Quote:


If I'm not wrong you are refering to :
Quote:


Well I read a lot of things about negative resistance on the internet (publications mostly) most of them stops at the gm_opt to have the best start-up time. I must admit that as most of them stopped their analysis with this tool at this point, I thought that there was nothing more.

About quartz litterature, you must be refering to :
Quote:


I think I found John Vig tutorial online (is it a powerpoint?).

If I wanted to fully understand the negative resistance approach for crystal oscillator, which book should I buy to do so?


Thank you for your help and sorry about asking the same questions over and over again, I think that it's still not clear for me.



EDIT : Have you got the titles of the books you advised me to read? I tried finding them online and one of them cost like 700 USD I hope it's not that one.


EDIT 2 : I think I found them all, but they cost a lot of money as an intern I'm not sure I can afford it.
The only book I can buy is :
Design of Crystal and other harmonic Oscillators by Benjamin Parzen. Will this book tell me enough about negative resistance?


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EDIT 3 :

Okay, I redid the negative resistance simulation by removing the quartz, adding a current source and the C0 of the quartz I'm using (5pF).
Small signal analysis :
The AC signal allowed me go get Re(amp) = -147 Ohm. The ESR of the quartz is 21.58 Ohm, therefore I have gain.
I got the X(amp) by plotting the imaginary part of the voltage drop across the quartz unit, X(amp) = -287 (Ohm?)
The phase calculated is Arctan(-287/-147) = 62.9°. Cadence told me that the phase was -117°, 62.9° - 180° = -117° so it's okay.

Now in order to determine the Re(amp) at steady state I need to run a large signal analysis. And the problem is here, how do I do that?
Do I put the crystal back?
Because if I don't, I don't think that the PSS analysis will converge at all. So my question is how do I simulate large signal analysis?

Thank you very much for your help.

I just want to thank you for your help, there is not much on the internet about how to fully and properly design a crystal oscillator and I was very lucky "to meet" you


EDIT :

Quote:


I understand that, it's just that I have no idea how to do a large signal analysis of the negative resistance.

I use a transient analysis on one pin of the current source, from the transient analysis I have a straight line of voltage. From what you said this voltage level should give me information on Re(Zin) and Re(Xtal).
Well, I extracted the real part of that signal using the "real" function in cadence, all I have is the exact same voltage level, therefore the imaginary part is 0, then I'm stuck.

I know it feels like I'm not listenning, thing is, I don't understand what I'm supposed to do when you say "do a large signal analysis"..... sorry about that. Anyway I'm going to read Parzen's book, I'm sure it will help, thank you.