Hello all, I wanted to design a dual power supply using two voltage regulators. I've gotten as far as trying to simulate the model but I don't think I'm on the right path. I would like some guidance in the right direction?

 

Normally this would be done by using a transformer with a centre tap on the primary. The centre tap form the common or "ground", the negative side of the bridge goes to the negative filter & regulator and the postive to the positive filter & regulator.

If you don't have a centre tapped transformer you can use half wave rectification, but that usually isn't very satisfactory except for low currents unless you use a lot of capacitance for the filters. Since the LT3012 can only handle 250 mA, half wave rectification could be workable.

Your bottom regulator must be a type designed for a voltage negative with respect to ground. I don't know if there is a negative voltage equivalent to the 3012. You can use a positive regulator for what is used as a negative voltage, but all of the circuitry must be completely separate from the positive side up to the point where you connect the positive output of one regulator to the negative of the other to form the output common. To do that you would have to have a transformer with two completely separate secondary windings, which is quite common now for small transformers, or use two separate transformers, which can be expensive, and two separate bridge rectifiers. This can actually be a good way to do things if you want a general purpose dual power supply because you can use them as two positive supplies, two negative supplies or one of each. Connecting them in parallel for higher current doesn't work well because they won't share current equally.

If you connect the a adj pin directly to the output, the regulator will produce 1.2 volts at the output. Normally you use a resistor voltage divider to set the output voltage you want. The LT3012 datasheet explains how to do that.

 

You can only do dual ±supplies from a single DC voltage if you use a regulator that can both sink and source current, such as the LT1118.
My write-up on doing that is here.

 

Depending what you want you can make a dual power supply with a center tapped secondary, a bridge rectifier,filter capacitors and two regulators as shown in the attached schematic