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gargoyle
Joined: 10 Oct 2004
Posts: 32
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 14 Dec 2004 17:46 questions about VCO with regulator |
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hello all:
i am designing a vco, the structure is regulator(bandgap+op), V-I converter and
CCO, but i found that even with noiseless power supply, the jitter of the vco is
much more worse than design the vco without regulator(only v-i converter and
cco). i am really confused.
wo should i think about the phenomena.
thanks
gargoyle
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simonkuo
Joined: 02 Nov 2004
Posts: 29
Helped: 2
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| 14 Dec 2004 19:02 Re: questions about VCO with regulator |
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Do you ever checked the regulator stability?
How many stage does your OP have?
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gargoyle
Joined: 10 Oct 2004
Posts: 32
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| 15 Dec 2004 4:39 Re: questions about VCO with regulator |
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yes，two stage,folder cascode OP,PM=60 .
the voltage for the internal supply is stable.
i found the reason, i check and measure the waveform by using SPICE EXPLORE,(simulator:hspice). and when i change the step of TRAN analysis, the
measure differs, and stable when tran step=0.05ns, (vco output freq about 1ghz )
it is really strange
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gargoyle
Joined: 10 Oct 2004
Posts: 32
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| 15 Dec 2004 12:46 Re: questions about VCO with regulator |
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does some one know how to configue the .OPTION command when
simulate oscillators?
thanks
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jswei303
Joined: 02 Nov 2004
Posts: 23
Helped: 1
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| 16 Dec 2004 9:44 Re: questions about VCO with regulator |
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have you checked your regulator's current supplied?
if the regulator cannot support enough current, it might cause the VDD noisy and this might be the reason I guess.
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