A feedback control loop in which the loop error is passed into three circuits that produce three outputs that are, respectively, proportional to the error, related to the time-integral of the error, and related to the time-derivative of the error. A weighted sum of these three outputs is used to determine the control signal. The tuning of a PID control is achieved by adjusting the weighting factors for the best control response. PID controllers are used where accurate, optimal control is required.