Subject: Re: basic VCO question.( test, frequency adjust, matlab)
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Date: Sat, 14 Dec 2002 18:00:11 GMT
NNTP-Posting-Date: Sat, 14 Dec 2002 13:00:11 EST
Organization: Cox Communications
"boki" wrote in message
> Hello thank you.
> this is a very basic VCO circuit/question.
> first question:
> Is this circuit correct?
Not if you want it to oscillate. Your basic oscillator structure is a ring
oscillator (M5,6,8,9), which has two inversions in the loop. If you add
another stage (M5,8 is one stage), it will oscillate.
However, it will only oscillate at one frequency.
I think you're trying to build a current-starved ring oscillator. If you
google for "current starved ring oscillator" (without the quotes), you'll
find circuits that look like what you're trying to design. Take care to
notice the differences.
> could you please tell me how to test this circuit ?
> If SPEC is:
> Frequency: > 100MHz
> Tuning range: > 10% or 20% or more
> could someone give me some hint?
Yes, but it sounds to me like you don't really know how the circuit works,
or where the inputs and outputs are. Take a look at the lecture notes by
Wilde in the google results. When you understand how it works, then you'll
know how to test it.
> the last question:
> [Output spectrum analysis using Matlab].<---- How to do that ? I never
> did that before... ><~
> I mean, how to get datas from SPICE and input it to Matlab?
In SPICE: .print v(oscillatornode)
Edit the text output file with your favorite text editor, or write a python
script to extract the data you want and put it in another file.
In MATLAB: load yourfilename.txt -ascii
-- Mike --