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Setting Up An Analysis
DC Mismatch
Related Topics
Monte Carlo Analysis
DC Mismatch
DC Sensitivity Analysis
AC Sensitivity Analysis
DC Mismatch
The .DCMISMATCH command runs a special form of sensitivity analysis based on statistical
deviation properties of device model parameters. It computes the sensitivity of node voltages
and of currents through voltage sources. All devices using a device model with statistical
deviations potentially contribute to the output deviation. The aim of the DC mismatch analysis
is to quantify these contributions and to identify the biggest contributors to the total output
deviation. It has some degree of similarity with the worst-case analysis (.WCASE). However, it
will usually provide (much) less pessimistic results than worst-case analysis.
Mismatch models try to model the inherent differences which exist between two identically
drawn transistors. Each transistor behavior departs (statistically) from the nominal behavior.
The deviation depends strongly on the geometry (W, L) of the transistor. Small transistors tend
to be more random than large ones.
DC mismatch considers the DEV or DEVX variations specified for device model parameters (in
.MODEL statements) and for global parameters in the .cir file (.PARAM statements specified at
the top-level, outside any subcircuit definition). Mismatch effects are ignored if DEV
specifications are associated to capacitance values (device or model parameters). The LOT
specifications are not taken into account.
Deviation is applied independently to the sensitive devices, and the resulting deviation of the
output is computed from the RMS sum of the resulting deviations.
Sorting parameters can be specified to quickly identify the most sensitive parameters.
Tip
See “.DCMISMATCH” in the Eldo Reference Manual.
DC Mismatch Results
Results of a DC mismatch analysis are provided inside the DC MISMATCH results section of
the .chi file.
Below is a typical DC mismatch analysis output showing N-sigma deviation of the outputs, and
a table of sorted contributors.
Eldo® User's Manual, 15.3 269