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  1. #1
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    PSpice Error subcircuit node is floating

    Hello,
    I have a simple circuit to test a varicap model in PSpice.
    Inside the varicap model seems to be a floating node.
    Any ideas how to fix this?
    The circuit is this:

    Click image for larger version. 

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    The varicap model is this:
    Code:
    .SUBCKT VARICAP 1 2 CTRL
    R1 1 3 1u
    VC 3 4
    EC 4 2 Value = { (1/v(ctrl))*v(int) }
    GINT 0 INT Value = { I(VC) }
    CINT INT 0 1
    .ENDS
    PSpice output with the error:
    *Libraries:
    * Profile Libraries :
    * Local Libraries :
    .LIB "../../../varicap.lib"
    * From [PSPICE NETLIST] section of U:\cdssetup\OrCAD_PSpice/16.6.0/PSpice.ini file:

    *Analysis directives:
    .TRAN 0 100us 0
    .OPTIONS ADVCONV
    .PROBE64 V(alias(*)) I(alias(*)) W(alias(*)) D(alias(*)) NOISE(alias(*))
    .INC "..\SCHEMATIC1.net"

    **** INCLUDING SCHEMATIC1.net ****
    * source VARICAPTEST
    V_V1 N00130 0 5Vdc
    R_R1 N00130 N00137 1k TC=0,0
    V_V2 N00170 0 1uVdc
    X_U1 N00137 0 N00170 VARICAP
    R_R2 0 N00170 1G TC=0,0

    **** RESUMING varicaptest.cir ****
    .END

    ERROR(ORPSIM-15142): Node X_U1.int is floating
    I think the internal node INT is driven only by a current source and might need a DC path (resistor) to GND.

    Any ideas how to fix this would be greatly appreciated.
    Thanks,
    - Wolfgang.

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  2. #2
    Newbie level 3
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    Re: PSpice Error subcircuit node is floating

    The solution was the standard answer for floating notes (add a very high value resistor (100 Mega ohm or more) between that floating node and ground), just in PSpice SUBCKT syntax. The working model looks like this:

    Code:
    .SUBCKT VARICAP2 1 2 CTRL
    R1 1 3 1u
    R2 2 INT 1G
    VC 3 4
    EC 4 2 Value = { (1/v(ctrl))*v(int) }
    GINT 0 INT Value = { I(VC) }
    CINT INT 0 1
    .ENDS
    Notice R2 is the high value resistor connected from INT (the internal node) to 2 (external node).

    Cheers, Wolfgang.



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