This article provides a few examples of using the built in Spice circuit elements to quickly and simply model circuits. These Spice primitives are also useful for filling in the rest of the environment when you want to concentrate on one piece, for example an input stage, without creating the entire schematic. This also allows you to examine performance of one part of the circuit in isolation, since the behavioral part will be "perfect."

The various Spice circuit elements are fully described in the help file underl LTspice > Circuit Elements.

AC to DC Power Supply
Vbe Multiplier and Temp Compensation