Dear Neda Mousavi,

I agree with Thomas. It is so that the floating nodes are that nodes with undetermined potential with respect to the reference node or the power supply node. If you have also two switches in series then the intermediate point between the two switches will be floating. This situation is similar to the two capacitors connected in series. The common node will be floating as hinted by Thomas.

The remedy of such a problem is to connect a high value resistance to this node either to the ground or the power supply node.

The simulator tells what are the floating nodes. Then you you can define their potentials by high value resistances that basically must not affect the operation of the circuit.

Best wishes

Dear Neda Mousavi ,

May be the best way to handle this circuit is to divide it into identical sub circuits.

Then run the simulation for each circuit. Sure trouble shooting sub circuits will be much easier to handle than the whole circuit.

This is the engineering appraoch to trouble shoot and operate the large circuits or systems.

Best wishes

Dear Abdelhalim abdelnaby Zekry

I am thankful with your guidance

Sincerely

Neda Mousavi

Hello Neda Mousavi ,

Usually, a floating node error is the result of one or more capacitors not having a connection on one of its leads (plates) referenced to a voltage node datum. For example, it looks like this might be the case with capacitors, C5, C9, C13, C17, C21, etc., where one lead is connected to an open switch. The easiest way to fix this problem is to parallel the capacitors with a high value resistor. Using a high resistance value resistor in parallel to a capcitor means that the transient response of the circuit will not be affected for times that are short in comparison to the RC time constant.

Does your version of SPICE tell you which nodes are the problem nodes? If the problem nodes are the ones associated with one lead (plate) of one of or more capacitors, then parallel these capacitors with the high value resistors. If SPICE does not tell you the problem nodes, then simply parallel all the capacitors in your circuit with high value resistors. Note, if both leads (plates) of a capacitor are floating, then connect each lead to a separate high value resistor, whose other end is connected to a datum node such as ground, common, or some other node with a known potential.

Note, in a real circuit, one likewise would always make sure that both leads of a capacitor are connected to either a pull-up or pull-down resistor. Of course, real capacitors all have a non-zero internal (parasitic) conductance (high resistance leakage resistor) shunting (in parallel with) the capacitor's dielectric, which may be sufficient to prevent the capacitor leads from floating.

Regards,

Tom Cuff

Dear Neda Mousavi,

I agree with Thomas. It is so that the floating nodes are that nodes with undetermined potential with respect to the reference node or the power supply node. If you have also two switches in series then the intermediate point between the two switches will be floating. This situation is similar to the two capacitors connected in series. The common node will be floating as hinted by Thomas.

The remedy of such a problem is to connect a high value resistance to this node either to the ground or the power supply node.

The simulator tells what are the floating nodes. Then you you can define their potentials by high value resistances that basically must not affect the operation of the circuit.

Best wishes