Fun with Sources

LTspice has several built-in dependant sources and behavioural models. The basic ones are named e, g, h, f, bv, and bi. We'll also go over some more interesting ways to use the basic voltage and current sources.
h - Current Dependant Voltage Source
f - Current Dependant Current Source
e - Voltage Dependant Voltage Source
g - Voltage Dependant Current Source
bv - Behavioral Voltage Source
bi - Behavioral Current Source

Here I'll be adressing the last four.

The voltage-dependant sources are very simple to use. Just right click on the component and change "Value" to whatever you want your gain to be. By using a negative number you can invert the input voltage.

The behavioral sources are a little more complicated, but still very simple once you know the syntax. The first thing you'll notice is that they only have the 2 terminals of their simple-source counterparts. This is because all of the behavioral modeling is done by combining arbitrary voltages and currents in a mathematical expression that you place in the "Value" field (after right-clicking on the part). This is another place where labeling nodes can be very helpful(Check the tutorial on subcircuits for more details). Lets say you have 2 nodes called V1 and V2. The expression
V=2*V(V1)+V(V2)
will cause the voltage sourced by the behavioral source to be the sum of V2 and twice V1. You can also use a whole host of mathematical functions, as well as creating a function of time. For a full list consult the help file under LTspice-->Circuit Elements-->B. Arbitrary behavioral voltage or current sources.

Now back to the basic sources we used before. It's very easy to modify those same DC sources to be used as AC. Just right-click on the source, then click the "Advanced" button. You can then set all kinds of parameters for the source.