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Question about VCO output

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Adam2008

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Hi All,

The amplitude of the output waveform of the Cross couled VCO is very large(6V) at begining, then it turned to be a equal amplitude waveform(0.8V ~ 1.6V), what could be the reason of the super large amplitude at the beginning?because of iniitial condition?

The output wavform is between 0.8V and 1.6V, how can I move it to between 0V and 0.8V? or between -0.4V and 0.4V?

Thanks.
 

khouly

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the inductor man . when u switch the on and off and there is an inductor there will be overshoot

khouly
 

    Adam2008

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Adam2008

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Thanks. khouly.

How can I solve this problem?
 

Mazz

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Usually not a big problem for two reason:
-Real Q is lower than schematic one, so real transient amplitude is lower
- it is very fast (few hundred of ns) and doesn't damage the transistors or reduce their reliability.

For DC scaling you can use an NMOS follower or DCblock and make a different bias.

I hope it can help.

Mazz
 

    Adam2008

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