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Design >> Analog Design >> Questions about differential pair ring oscillator
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Message started by Coolway on Oct 9^th, 2022, 8:34pm

Title: Questions about differential pair ring oscillator
Post by Coolway on Oct 9^th, 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.

Title: Re: Questions about differential pair ring oscillator
Post by Ken Kundert on Oct 9^th, 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.