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.
我最近也遇到了类似的问题。可以看看这本书《THE DESIGNER'S GUIDE TO SPICE AND SPECTRE》的40页,“The gmin conductors affect the accuracy of the solution because they change the circuit being solved by the simulator. Most circuits are tolerant of the small currents that fow through the gmin conductors, however some circuits are not. For example, sample-and-hold circuits or other circuits that try to hold charge on a capacitor for a longperiod of time are sensitive to the small currents that fow through the gmin conductors. Spectre warns you if the current through the gmin conductors is adversely affecting the accuracy of the solution and allows you to set gmin to zero. ”。简单地说spectre仿真器为了方便电路的收敛在电路仿真的时候会在节点上加入额外的电阻,以gmin=1pS+NMOS的衬底接地+源极电压为1V这种情况为例,这意味着ISB将会额外增加1pA。这将会大于源和衬底之间的反偏PN结电流。