# Is it possible to analyse crossed coupled oscillator this way?

Discussion in 'Homework Help' started by screen1988, Apr 13, 2013.

Mar 7, 2013
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2. ### screen1988 Thread Starter Member

Mar 7, 2013
310
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Now I will ask more specific question and hope someone can help.
For example at first both capacitors and inductors are charged.
Why do you know that at a time there is only one transistor is ON?

3. ### Jony130 AAC Fanatic!

Feb 17, 2009
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4. ### screen1988 Thread Starter Member

Mar 7, 2013
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Aha, I have never thought about that
How can you know that when M1 is ON Vds1 is very small that is not enough to open M2?
How can you calculate Vds1?

5. ### Jony130 AAC Fanatic!

Feb 17, 2009
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We know that because there is a very strong positive feedback in this type of a circuit.
For example if voltage at point Y is increasing the M1 will be "more open".
This means "more" will current flow through Rp1. So there will be more voltage drop across Rp1 resistor. So the Vsd1 voltage will be drop (at point X). And this will reduces M2 current. And voltage at point Y will increase even more. And voltage at point X will be further decreases and so on.

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6. ### screen1988 Thread Starter Member

Mar 7, 2013
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Thanks, I see that it is a bit like differential amplifier.
But what happen after that? I can't see that how the circuit oscillate?

7. ### Jony130 AAC Fanatic!

Feb 17, 2009
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No, this circuit has nothing to do with the differential amplifier.
The tank circuit helps.
http://class.ee.iastate.edu/djchen/ee507/VCO.pdf

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