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Questions about differential pair ring oscillator (Read 56 times)
Coolway
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Questions about differential pair ring oscillator
Oct 09th, 2022, 8:34pm
 
I'm currently designing a 4-stage differential pair ring oscillator and I encounter several questions:
1. When I do TRAN simulation, I have to set the Options→maxstep to 0.1ps, otherwise the circuit will not oscillate. When I do PSS simulation, it can draw f/V curve. I wonder whether my circuit is working normally. There is no start-up circuit, btw.
2. My oscillation frequency is around 700M-1.3GHz, while my KVCO is 1GHz/V. I think it is too large. Is there any good methods that can decrease KVCO of a ring oscillator? my circuit structure is shown below.
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Ken Kundert
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Re: Questions about differential pair ring oscillator
Reply #1 - Oct 9th, 2022, 10:39pm
 
10,000 points per cycle is much more than you need.  It would be better to provide a mechanism for starting the oscillator.  A differential initial condition is a good way to go.  A short duration differential source is also good.
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