Electrical – I have been trying to simulate this but it won’t and it gives me those 2 errors

Not a PSpice user so I can't comment there, but here's how it's done in LTSpice. I assumed you wanted a voltage source instead of a current source as you've drawn it, but your post isn't very clear. The following instructions will also work for a current source.

First, make the schematic, setting the voltage on the source to "AC 1":

Then, create the simulation by going to Simulation -> Edit Simulation Command. I did a sweep from 1 Hz to 1 MHz in 100 pts/decade.

Now you can click the output node to get the Bode plot:

Hope this helps.

Side note: as your circuit is purely reactive, the gain is very large at resonance. This is voltage gain only - this is a passive network and cannot exhibit any power gain. To demonstrate this, try assigning an impedance to the source and loading up the output.

Yes, the standard workaround is just like that. My problem was that an internal node inside a component had this floating node error. The solution was the same, just in PSpice SUBCKT syntax. The working model looks like this:

.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.