WIDTH CONTROLLED SAMPLIER PULSING A SAMPLE-HOLD THEREBY EFFECTING A LOW-PASS FILTER FOR A SAMPLE-DATA SERVO

Servo systems may be subject to disturbances if they respond to signals above a certain frequency, if for example, the frequency is related to the natural resonance of the mechanical portion of the servo system. Filters have been used in the past to eliminate this source of instability. The present invention discloses a simple electronic circuit which operates as a filter suitable for use in certain servo systems, specifically of the sample-data servo type. The circuit includes a sample-hold capacitor which is larger than normal whereby it may not charge fully during a single sample period if the sampling pulse is varied in width. Thus, several sample periods may be necessary before the sample-hold capacitor is fully charged and the effect of this circuit is similar to introducing a low-pass filter into the servo system.