Editing Proportional–integral–derivative controller (section)

===Electronic analog controllers===
Electronic analog PID control loops were often found within more complex electronic systems, for example, the head positioning of a [[disk drive]], the power conditioning of a [[power supply]], or even the movement-detection circuit of a modern [[seismometer]]. Discrete electronic analog controllers have been largely replaced by digital controllers using [[microcontrollers]] or [[FPGA]]s to implement PID algorithms. However, discrete analog PID controllers are still used in niche applications requiring high-bandwidth and low-noise performance, such as laser-diode controllers.<ref name="Toptica">{{cite web|url = http://www.toptica.com/fileadmin/user_upload/Articles_Application_Notes/toptica_AP_1012_laser_locking_2012.pdf|last = Neuhaus|first = Rudolf|title = Diode Laser Locking and Linewidth Narrowing|access-date = June 8, 2015}}</ref>