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spectre says "The following branches form a loop of rigid branches "

eashwar g

there is no connection to the particular node...which spectre is listing . i dont know why it keeps pointing out the error . please check this

Fatal error found by spectre during topology check.
    FATAL: The following branches form a loop of rigid branches (shorts) when added to the circuit:
        I16:w_position_flow (from state to 0)

but as per my circuit that connection is must .. so suggest possible solution


  • with the circuit as shown in fig1 it simulates without errors

    ill post the circuit which is showing errors in next comment

  • in this fig ..i hav just used copied the above circuit ..so wen i start spectre simulation it says rigid loops error ..y is this happening with multiple circuits

    there is no connection between the 2 circuits ., then how come it starts up error .. please suggest some solution

  • There are in fact many connections between the two circuits, because wires (and pins) labeled with the same name are connected.

  • In addition to what Frank says, this message is telling you that you have multiple voltage (or potential) sources in parallel, and is a check that is done because there can be no solution to the equations in this case (think of having two ideal voltage sources with different potentials in parallel - what would the voltage across them actually be?)

    Regards,

    Andrew.

  • thank u frank and Andrew for your advice .,i need to use both the sources for that component so i need to put those two sources one is inverted and other is non inverted input .,As per my design i am supposed to use both so please suggest some solution to this problem if i create a component with 3 pins a,b,c and i use that component twice as shown in figure ....will there be any issues i mean the second component with pins a,b,c accepts the same voltage and current as that of the first component. i hope you understand what I am trying to convey.. regards eashwar

  • Use different names for the wire labels (and the pins) in the two parts of the circuit.

  • No, I don't understand what you are trying to convey.
  • thank u frank and Andrew for your advice .,i need to use both the sources for that component so i need to put those two sources one is inverted and other is non inverted input .,As per my design i am supposed to use both so please suggest some solution to this problem if i create a component with 3 pins a,b,c and i use that component twice as shown in figure ....will there be any issues i mean the second component with pins a,b,c accepts the same voltage and current as that of the first component. i hope you understand what I am trying to convey.. regards eashwar
  • if we have a transistor with pins g,d,s 1) if i connect a voltage source to pin g and plot vi char 2)similarly in same schematic i create another transistor with same pins g,d,s and plot vi char will there be any issues 3)the problem is the component i created is in veriloga so for a current it would be I(p,n) if i have to change pin names then i have to modify whole code 4)this is the problem i am facing
  • the problem is the component i created is in veriloga so for a current it would be I(p,n) if i have to change pin names then i have to modify whole code

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