Mohsenkma
New Member
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Posts: 6
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Hi Mr. Kundert,
Thank you for your response and excuse me for my delayed reply. I have executed a lot of simulations and changed many parameters. Finally, I found that this problem is arisen when relatively big capacitors (e. g. 200 fF) are used in switched-capacitor bank. I changed the capacitors of switched-capacitor bank from MOSCAP to MIMCAP, but the problem still existed. I increased the negative resistance of cross coupled transistors but it didn't help. I use both PSS analysis (harmonic balance) and transient analysis. I run transient analysis for 10 μsec to be sure that the steady-state regime has been reached. The state of switches doesn't change during the analysis. I don’t know why big capacitors have such an effect on my circuit but to solve the problem, I use capacitors below 30 fF in the switched-capacitor bank, therefore, the method used to start the oscillator is no more influential on the frequency and amplitude of the oscillation.
Thank you for your consideration,
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