• Generate scanning signals for the x-y piezo
• Take an input signal from the force sensor and then generate control voltage for the Z piezo
• Output control signals for X-Y-Z stepper motors
• Generate signals for vibrating the probe and measuring phase or
  amplitude when vibrating mode is used for scanning
• Collect signals for display by the computer
  

The following sections are a detailed description of these functions.

FIGURE 2-26 Block diagram of the functions in an AFM electronic controller as implemented with analog electronics.

As mentioned above, these functions may be implemented with either digital or analog electronics. In the digital approach, see Figure 2-27, all signals from the stage are digitized, and a DSP chip takes care of all of the feedback control calculations. Also, the DSP chip generates the x-y raster scan functions. The advantage of analog electronics is that they are typically less noisy. Because the functionality of a DSP chip is created by a software program, the DSP approach gives a little more flexibility and can be changed very rapidly.