sheldon
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Vivek,
There is an app note that includes a detailed discussion
of dc mismatch and information on how to derive mismatch
models. Some clarifications:
1) You can think of dc mismatch analysis as the equivalent
of corner analysis for device mismatch. It introduces a
3-sigma mismatch between matched devices and allows
designers to determine whether the design passes or
fails with mismatch.
2) DC mismatch reports the effect of the device mismatch,
for example, the offset voltage of the device.
3) In addition, it reports the "root cause" of the problem
so that designers can improve the design. This is the
purpose of the sensitivity outputs. The report also
includes some insight into the source of the mismatch,
for example, Vt, Beta, ...
--> Information is helpful in understanding how to
improve the design.
4) The "threshold" parameter is used to allow designers
to ignore pairs that don't make a big contribrution
to the output. This is helpful when analyzing large
designs.
5) Designers do not vary the parameters, models including
dc mismatch need to be provided by the foundry. In the
app note there is a description of how to derive the
required model parameters.
6) You can save the dc operating and use it with the
small signal analysis. So you can calculate the effect
of mismatch on common-mode rejection and
power supply rejection.
DC mismatch analysis is being actively enhanced. Recently
gummel-poon bipolars and the EKV model were added
to the analysis.
DC mismatch is also very useful for verification and synthesis.
Best Regards,
Scheldon
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Using dcmatch analysis in Spectre (Read 9410 times)