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amitbhaiji
Joined: 19 Jan 2004
Posts: 67
Helped: 1
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 20 Jan 2004 9:29 Wander in RC Oscillator. |
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Hi, I am designing a RC Based oscillator with the ocillation frequency of 1.5Mhz. problem which i am seeing with this circit is that its ouput frequency is wandering by about 150Hz around the center frequency ( Ouptput frequency variation is very slow with respect to time. Can any one suggest me the reason for the same.
and how can i reduce it.
Amit
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PaulHolland
Joined: 15 Jan 2003
Posts: 637
Helped: 59
Location: Holland
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20 Jan 2004 10:19 Re: Wander in RC Oscillator. |
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Hi,
What net frequency are they using in your country ?? if its 60 Hz then the frequency change could be 120 Hz... What R are you using in your RC osc ??..
try to reduce the R if its larger than 50K.. it is possible that your power supply is not clean and that a small signal of 120 Hz is there... try to power your device by batt and see the result .
regards,
Paul.
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amitbhaiji
Joined: 19 Jan 2004
Posts: 67
Helped: 1
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20 Jan 2004 11:06 Re: Wander in RC Oscillator. |
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oops! Sorry i forget to mention that nearly same wander i am obtaining with my transistor level simulation. So as you predected that the coupling
is not the cause of this drift.
Thsi design is just like the 3 stage ring oscillator with inverter being replaced by the comparator whose other input is from the bandgap refernce source... What i am predicting is " That the upconversion of the flicker noise of bandgap is major contributor towards this drift"
what you feel
Amit
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zhaoshibin
Joined: 11 Oct 2006
Posts: 44
Helped: 2
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22 May 2007 2:50 Wander in RC Oscillator. |
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| I have also been puzzled by the OSC design,does anybody have some good material about that?
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22 May 2007 2:50 Ads |
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alexandr22061986
Joined: 16 May 2007
Posts: 167
Helped: 8
Location: Ukraine
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26 May 2007 19:08 Re: Wander in RC Oscillator. |
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| For increasing stability you can use instead of RC circuit a quartz resonator that have narrow resonant characteristic
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rogerynt
Joined: 06 Mar 2007
Posts: 109
Helped: 11
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29 May 2007 5:56 Re: Wander in RC Oscillator. |
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| Can you show us the the circuit ?
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