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how to obtain negative resistance for VCO oscillation?

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slienteyes

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I just try to simulate the transistor with common base topology with inductor as feedback in base in order to get the negative resistance which means make K<1 and S11,S22>1.

But I don't know what the correct way to optimize the transistor to get the negative resistance. This is the normally first step to design LC oscillator, isn't it?

Thanks for reply!
 

In Negative Resistance VCO if the bias conditions in emitter/source resistance are below ~200 ohms, an RF choke may be required in series with this resistance.
If high Ft transistor is used, also requires increasing the capacitance added to emitter/source.
 

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