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How to fix warning from Spectre about a missing bulk-source and bulk-drain diode?

Bean Nakamura

Hello guys,

I ran a transient analysis on the attached circuit and Spectre gave the following warnings:-

Warning from spectre at time = 120.665 us during transient analysis `tran'.
WARNING (CMI-2151): M0.main: Missing bulk-drain diode would be forward biased.
Notice from spectre at time = 120.665 us during transient analysis `tran'.
M0.main: Missing bulk-drain diode returns to normal bias condition.
Further occurrences of this notice will be suppressed.

How do I fix this warning? What does the warning even mean? Will it effect my simulations?
The circuit was simulated using Silterra Technology.

Thanks!

Parents
  • ImanKian

    Spectre(R) Circuit Simulator User Guide
    Product Version 5.0
    July 2002

    [page 259, First paragraph]

    Most p-n junctions in semiconductor models include both a resistive (the diode) and a capacitive (the junction capacitance) model. If the diode reverse saturation current is set to zero, the resistive part of the junction is turned off, and the Spectre simulator assumes that the resistive portion of the junction does not exist (but the junction capacitance may still be present). In this case, if the voltage across the missing diode is larger than 10 * Vt (where Vt is the thermal voltage), Spectre will issue a warning message telling you that the junction, which is missing, will be forward biased. A follow-up notice is issued if, and when, the device returns to a normal bias condition
Reply
  • ImanKian

    Spectre(R) Circuit Simulator User Guide
    Product Version 5.0
    July 2002

    [page 259, First paragraph]

    Most p-n junctions in semiconductor models include both a resistive (the diode) and a capacitive (the junction capacitance) model. If the diode reverse saturation current is set to zero, the resistive part of the junction is turned off, and the Spectre simulator assumes that the resistive portion of the junction does not exist (but the junction capacitance may still be present). In this case, if the voltage across the missing diode is larger than 10 * Vt (where Vt is the thermal voltage), Spectre will issue a warning message telling you that the junction, which is missing, will be forward biased. A follow-up notice is issued if, and when, the device returns to a normal bias condition
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