大家帮忙看看DC仿真出现这句话是什么意思？

CmosLgh

大家帮忙看看DC仿真出现这句话是什么意思？


就是单纯的用spectre进行运放的直流仿真时，仿真没有问题但是报告中总是有这句话出现，是啥意思求解答？

我的解放日志

"Bad pivoting is found during DC analysis" 是Cadence Spectre仿真报告中可能出现的错误信息。这个错误通常是由于仿真过程中发现了矩阵奇异性或者数值不稳定性导致的。

这个问题可能有多种原因，以下是一些可能的解决方法：

1. 检查电路连接和元件模型：确保电路连接正确，并且使用的元件模型是准确的。错误的连接或者不合适的模型可能导致数值计算问题。

2. 调整仿真参数：尝试调整仿真的参数，例如步长、容忍度等。减小步长或者增加容忍度可能有助于解决数值不稳定性的问题。

3. 检查初始条件：检查仿真的初始条件是否合适。有时候，不合适的初始条件也会导致数值计算错误。

4. 优化电路设计：如果以上方法都没有解决问题，可能需要优化电路设计。这可能包括修改电路拓扑、改变元件参数等，以使仿真更加稳定。

如果以上方法都无法解决问题，建议参考Cadence Spectre的文档或者向Cadence技术支持寻求帮助，他们可以更具体地指导你如何解决这个错误。（chatGPT说的）

CmosLgh

我的解放日志 发表于 2023-7-13 10:07
"Bad pivoting is found during DC analysis" 是Cadence Spectre仿真报告中可能出现的错误信息。这个错误通 ...

大哥，上面这段话都是chatGPT说的吗？苦笑

好像不论怎么调电路，这个错误信息一直有，但是电路仿真是对的啊，还是说仿真model有什么问题呢

我的解放日志

CmosLgh 发表于 2023-7-13 11:13
大哥，上面这段话都是chatGPT说的吗？苦笑

好像不论怎么调电路，这个错误信息一直有，但是电路仿真是对 ...

都是它说的。电路仿真是对的应该就没啥问题吧，我瞎说的

CmosLgh

我的解放日志 发表于 2023-7-14 09:07
都是它说的。电路仿真是对的应该就没啥问题吧，我瞎说的

虽然仿真没有问题，但我感觉 Bad pivoting 可能是一个潜伏的隐患，看看大家有没有遇到过？

CmosLgh

再顶一下，有没有人和我一样？

CmosLgh

Opening the PSF file ../psf/dc.dc ...
Important parameter values:
    reltol = 1e-03
    abstol(V) = 1 uV
    abstol(I) = 1 pA
    temp = 25 C
    tnom = 27 C
    tempeffects = all
    gmindc = 1 pS

Notice from spectre at VDDA = 0 during DC analysis `dc'.
    GminDC = 1 pS is large enough to noticeably affect the DC solution.
        dV(AMP.M18:int_d) = -1.84716 V
        Use the `gmin_check' option to eliminate or expand this report.
    Bad pivoting is found during DC analysis. Option dc_pivot_check=yes is recommended for possible improvement of convergence.
Notice from spectre at VDDA = 36e-03 during DC analysis `dc'.
    GminDC = 1 pS is large enough to noticeably affect the DC solution.
        dV(AMP.M18:int_d) = -2.33759 V
        Use the `gmin_check' option to eliminate or expand this report.
    Bad pivoting is found during DC analysis. Option dc_pivot_check=yes is recommended for possible improvement of convergence.
Notice from spectre at VDDA = 72e-03 during DC analysis `dc'.
    GminDC = 1 pS is large enough to noticeably affect the DC solution.
        dV(AMP.M18:int_d) = -1.9965 V
        Use the `gmin_check' option to eliminate or expand this report.
    Bad pivoting is found during DC analysis. Option dc_pivot_check=yes is recommended for possible improvement of convergence.

    dc: VDDA = 72e-03         (4 %), step = 36e-03          (2 %)

CmosLgh

Warning from spectre during hierarchy flattening.
    WARNING (SFE-884): "/home/work/MacroLee/smic018bcd_OA/018UM/SPDK018V3EBCD_18506090120160200240300350400_OA_CDS_CalxRC_V1.0_REV1_0/smic18v3ebcd_1P4M_TM2_HRP1k_MIM2_TYP1_oa_cds_calxrc_v1.0_rev1_0/./models/spe/d18_v3e_bcd_v1p0_rev1_spe.lib" 42: The option 'gmin' is deleted because it is redefined at 'input.scs':line '126'.
    WARNING (SFE-884): "/home/work/MacroLee/smic018bcd_OA/018UM/SPDK018V3EBCD_18506090120160200240300350400_OA_CDS_CalxRC_V1.0_REV1_0/smic18v3ebcd_1P4M_TM2_HRP1k_MIM2_TYP1_oa_cds_calxrc_v1.0_rev1_0/./models/spe/d18_v3e_bcd_v1p0_rev1_spe.lib" 4952: The option 'gmin' is deleted because it is redefined at 'input.scs':line '126'.
    WARNING (SFE-884): "/home/work/MacroLee/smic018bcd_OA/018UM/SPDK018V3EBCD_18506090120160200240300350400_OA_CDS_CalxRC_V1.0_REV1_0/smic18v3ebcd_1P4M_TM2_HRP1k_MIM2_TYP1_oa_cds_calxrc_v1.0_rev1_0/./models/spe/d18_v3e_bcd_v1p0_rev1_spe.lib" 8850: The option 'gmin' is deleted because it is redefined at 'input.scs':line '126'.
    WARNING (SFE-884): "/home/work/MacroLee/smic018bcd_OA/018UM/SPDK018V3EBCD_18506090120160200240300350400_OA_CDS_CalxRC_V1.0_REV1_0/smic18v3ebcd_1P4M_TM2_HRP1k_MIM2_TYP1_oa_cds_calxrc_v1.0_rev1_0/./models/spe/d18_v3e_bcd_v1p0_rev1_spe.lib" 10002: The option 'gmin' is deleted because it is redefined at 'input.scs':line '126'.
    WARNING (SFE-884): "/home/work/MacroLee/smic018bcd_OA/018UM/SPDK018V3EBCD_18506090120160200240300350400_OA_CDS_CalxRC_V1.0_REV1_0/smic18v3ebcd_1P4M_TM2_HRP1k_MIM2_TYP1_oa_cds_calxrc_v1.0_rev1_0/./models/spe/d18_v3e_bcd_v1p0_rev1_spe.lib" 10129: The option 'gmin' is deleted because it is redefined at 'input.scs':line '126'.
        Further occurrences of this warning will be suppressed.

Myjia

仿真的是运放吗？什么结构方便放出来吗？

tracy6969

interesting