Simulating a current load in LTSpice

[electrophile]

Hi, I'm working on designing a LM1085 based voltage regulator that gives out 12V at 3A. I've attached the LTSpice schematic here. Everything works fine and I can see a nice clean 12V too but can anyone please help me with simulating this at a current load of 2A? I tried the load from the LTSpice library (and selected this is an active load) but when I do that, everything goes wonky.

 

[FvM]

It's exactly what happens in a real circuit when the AC input voltage (or the capacitor) is too low. Do you understand that 15V magnitude in sine source refers to peak value corresponding to about 10.6 Vrms?

 

[electrophile]

Didnt know that FvM! Thanks. The 15V AC source was supposed to simulate the transformer secondary output that feeds into the bridge rectifier. So how do I correct this schematic now?

 

[FvM]

15 VAC (Vrms) means peak voltage of 21.2V, isn't it?

 

[electrophile]

Yep it is. I entered this value on the voltage source and now it seems to be simulating properly with a load of 2A. Also I increased the value of the input capacitor to 6800uF. Thanks!!

I tried powering a LM317 regulator from this 12V regulator and that does not seem to be working with similar conditions. Any ideas?