This is an example of a closed loop system. A microcontroller, FPGA, or other DSP controller is initially programmed with the set-point. The controller then sets the digital code into an LTC2601 single output DAC. Next, the DAC output voltage is amplified through a power amplifier to provide the required drive current to the motor. At the next stage of this closed loop system, a tachometer is used to measure the rotational speed of the motor. The rotation signal is the actual output, or process variable, of the closed loop system. An ADC digitizes the tachometer’s output and sends the data to the controller, where an algorithm determines if any correction needs to be made at the DAC output, and ultimately, the motor. In this way, the error is reduced to an acceptable level. Feedback ideally allows the closed loop system to cancel out all errors, effectively limiting the effects from any errant sources of noise, temperature, force, or other unwanted signals. It is vital that the selected DAC is monotonic, which means DNL must be greater than -1. If the DAC is not monotonic, there will be a region where negative feedback turns into positive feedback. This can lead to oscillation that may eventually destroy the motor.