Stats

  • Locked Locked
  • Replies 9
  • Subscribers 126
  • Views 17877
  • 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

Why gm is not zero even when iDS is a constant DC current?

BaaB

I am trying to plot transconductance gm of M0 in the picture below. However, what I am supprised here is why gm is not zero when iDS is a constant DC current (1uA).

gm = diDS/dvGS

So according to this, gm should be zero when iDS is a constant.

As seen from the picture below, gm is not zero.

Could anyone explain why and how gm is calculated by the simulator?

Thank you.

Parents
  • awesome1

    Your test circuit is not correct.  

    As others have said, the transconductance (gm) is a small-signal parameter that is extracted at any operating point.

    gm should not be zero under constant DC bias--in fact, DC bias is needed to extract gm.

    You should do a small-signal extraction of parameters. There are several ways to do that.

Reply
  • awesome1

    Your test circuit is not correct.  

    As others have said, the transconductance (gm) is a small-signal parameter that is extracted at any operating point.

    gm should not be zero under constant DC bias--in fact, DC bias is needed to extract gm.

    You should do a small-signal extraction of parameters. There are several ways to do that.

Children
No Data

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.