This page presents a simulation a simplified copy of the Linisteppers drive circuit with the goal of helping students to understand how it works, what each part of the circuit does, and the advantages provided by each part. It makes use of the excellent circuit simulator from http://www.falstad.com.
You can move your mouse over the different parts of the circuit and the status, voltage, current, etc... for that component will be displayed in the lower right corner. For example, if you mouse over the first (left hand) transistor, you can see that when the coil is off, the transistor will be in "cutoff": not allowing any current to flow into the coil. When the next step begins, the transistor quickly transitions into "saturation" meaning that it is fully on and allowing as much current as possible, at nearly the full supply voltage, to flow into the coil, bringing the coil and so the magnetic field around the coil to full strength as quickly as possible.
The graphs in the lower area show the power and current flow through the coil.
There are switches on the three major parts of the circuit, which you can click on to open or close. These allow you to disable the different circuit parts and see what advantage they provide for the Linistepper design.
Switching the power supply for the coil (motor) voltage from 12 to 5 volts shows how slowly the current builds up in the coil when it is operated at only its rated voltage.
Shorting out the current sense resistor in the lower right area causes the current to rise beyond what is safe for the coil, especially when using a higher voltage supply.
Disconnecting the smoothing capacitor on the left side points out the effect it has on the coil drive signal; when it is connected, the waveform is much closer to the ideal sinewave.
The old Java only version is still available The simulation does require Java, which is available for most operating systems and browsers from http://www.java.com