Sensitivity Analyses (sens)

Description

Use the sens control statement to find partial or normalized sensitivities of the output variables with respect to component and instance parameters for the list of the analyses performed. Currently, DC and AC sensitivity analyses are supported. The results of the sensitivity analyses are stored in the output files written in Cadence Parameter Storage Format (PSF). The global option parameter senstype (see the options statement) is used to control the type of sensitivity being calculated. In addition, you can use +sensdata filename command-line argument or a global option (see the options statement) to direct sensitivity analyses results into a specified ASCII file.

Definition

sens (output_variables_list) to (design_parameters_list) for (analyses_list)

where:

• output_variables_list = ovar1 ovar2, and so on.
• design_parameters_list = dpar1, dpar2, and so on.
• analyses_list = anal1 anal2 , and so on.

The list of design parameters may include valid instance and model parameters. You can also specify device instances or device models without a modifier. In this case, Spectre attempts to compute sensitivities with respect to all corresponding instance or model parameters. Caution should be exercised in using this option as warnings or errors may be generated if many instance and model parameters cannot be modified. If no design parameters are specified, then all the instance and model parameters are added. The list of the output variables for both AC and DC analyses may include node voltages and branch currents. For DC analyses, it may also include device instance operating point parameters.

Examples

• sens (q1:betadc 2 Out) to (vcc:dc nbjt1:rb) for (analDC)
  For this statement, DC sensitivities of betadc operating point parameter of transistor q1 and of nodes 2 and Out are computed with respect to dc voltage level of voltage source vcc and model parameter rb for the DC analysis analDC. The results are stored in the raw directory with the name in the format analysisname.sens.analysistype, that is, dc.sens.analDC.
• sens (1 n2 7) to (q1:area nbjt1:rb) for (analAC)
  For this statement, AC sensitivities of nodes 1, n2, and 7 are computed with respect to the area parameter of transistor q1 and the model parameter rb for each frequency of the AC analysis analAC. The results are stored in the output file analAC.sens.ac.
• sens (1 n2 7) for (analAC)
  For this statement, AC sensitivities of nodes 1, n2, and 7 are computed with respect to all instance and model parameters of all devices in the design for each frequency of the AC analysis analAC. The results are stored in the file in the format ac.sens.analAC.
• sens (vbb:p q1:int_c q1:gm 7) to (q1:area nbjt1:rb) for (analDC1)
  For this statement, DC sensitivities of branch current vbb:p, the operating point parameter gm of the transistor q1, the internal collector voltage q1:int_c and the node 7 voltage are computed with respect to instance parameter area for instance q1 and model parameter rb for model nbjt1.

For additional information, see Sensitivity Analysis in the Spectre Classic Simulator, Spectre APS, Spectre X, and Spectre XPS User Guide.

Options for Sparam Standalone Checking and Fitting Tool (sparam)

Description

• +checking - Checking quality of original S-parameter data including:
  • DC point: Checking if DC points are provided, and also DC imaginary is zero.
  • Fmax: Reporting maximum freq in the data.
  • Fmin: Reporting minimum freq in the data after DC point.
  • Reciprocity: Reporting if S-parameter matrix is symmetric.
  • Discontinuity in Real/Imaginary: Reporting S-parameter elements with discontinuity in either real or imaginary part.
  • Discontinuity in Phase: Reporting S-parameter elements with discontinuity in phase.
  • Data rotation in Polar coordinate system: Reporting S-parameter elements with counter-clockwise rotations and possible causality issue.
  • Passivity: Checking S-parameter data passivity. Absolute tolerance of passivity criteria is 1e-6.
• +fitting [=rfm]
  • 'rfm': only generates rational fitted model.
• +multithread=<N> - Enables the multithreading capability, where, N is the number of threads specified. A maximum of 64 threads are allowed.
  • '+mt' can be used as an abbreviation of '+multithread'

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