Yes, it has sense because it is not a physical inductance but the model parameter only.2.does a 6.9KiloHenry inductance in crystal model too large to make sense?
simao said:hi Fom, thanks for your help!
but how can i do the open loop ac analysis, i did it like this: put a vdc source between inverter input and the crystal, and set the dc value equal to 0 and ac value equal to 1, and then run a ac simulation, finally calculate vout/vin(where vout and vin is minus and plus terminal of the vdc source respectively). then i got a bode plot and attached below, but i doubt if this method is correct, because from the bode plot i find the gain at the frequency where phase euqals to 0 is always larger than 0dB but the oscillator can't oscillate any way. If the method is not correct can you give me a method to simulate the open loop ac gain and phase.
thank you
Added after 10 minutes:
Oscillator simulation needs a external stimuli to spur the ckt to amplifier the noise component of resonant frequency in Spectre simulation.
this is the ac gain and phase i got.
buckaroo said:
buckaroo said:这个地方好象影响应该不大。
不过我的老是振荡不起来啊,衰减的,不知道怎么回事,头疼……
simao said:hi Ryan,
i use this inverter structure for control the current it consumpted. what about frequency of your oscillator, does it 32.768KHz? and where do you get the crystal model. the parameter of crystal model i used is calculated and i don't know whether it correct or not. can you give me some suggestion?
thanks very much.
the simulator i used is spectre, and i set a vpulse to startup, but failed except only 1 time, and i belive my ckt is able to oscillate, how to setup the initial current of the inductor.jfyan said:buckaroo said:这个地方好象影响应该不大。
不过我的老是振荡不起来啊,衰减的,不知道怎么回事,头疼……
hi
1. pay attaintion to your option setup in spice.
2. reduce the resistance in crystal equivalent ckt to see wethether the oscillation build up stablly;
3. reduce the load capacitance to,saying, 10pF. BOTH the load capacitance, and resistance will overdamp or kill the crystal's oscillating, if they are too large.
good luck
\jeff
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