• Skip to main content
  • Skip to search
  • Skip to footer
Cadence Home
  • This search text may be transcribed, used, stored, or accessed by our third-party service providers per our Cookie Policy and Privacy Policy.

  1. Community Forums
  2. Custom IC Design
  3. Effect of load capacitor at the output of an oscillator

Stats

  • Locked Locked
  • Replies 3
  • Subscribers 126
  • Views 13653
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Effect of load capacitor at the output of an oscillator

Jithin
Jithin over 13 years ago

Hi,

While designing an oscillator ,which had a ring oscillator(differential ended) architecture , the frequency sensitivity of the vco had changed, that is if initially my vco works in a frequency range of 300MHz - 500MHz aor a control voltage range (1.3V-1.85V). After adding a capacitor

at the output,say 400fF of each differential amplifier stage then the same frequency(300MHz- 500MHz) swings at a voltage range of (.9V - 1.65V).Thereby decreasing the  gain of vco. The problem is that I can't find a reason for this phenomenon and can't answer the questions like how the range of the control voltage had changed due to the addition of a load capacitor.

Please help me.

Thanking you in advance.

with regards,

Jithin 

  • Cancel
  • Quek
    Quek over 13 years ago

    Hi Jithin

    It seems that this is a design issue and it would be a little hard for us to help. : )  Hope that you will be able to get more help in the designer's forum.

    Best regards
    Quek

    • Cancel
    • Vote Up 0 Vote Down
    • Cancel
  • Andrew Beckett
    Andrew Beckett over 13 years ago

    Especially without seeing the design - you didn't even say how the control voltage controls the VCO frequency, for example. But Quek's right - a more design-centric forum would probably make more sense.

    Andrew.

    • Cancel
    • Vote Up 0 Vote Down
    • Cancel
  • Jithin
    Jithin over 13 years ago
    Thank you Andrew .
    • Cancel
    • Vote Up 0 Vote Down
    • Cancel

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.

© 2025 Cadence Design Systems, Inc. All Rights Reserved.

  • Terms of Use
  • Privacy
  • Cookie Policy
  • US Trademarks
  • Do Not Sell or Share My Personal Information