| 摘要 |
<p>An active filter separates the function of a principal feedback loop which provides velocity error correction from that of a nested feedback loop which provides video signal frequency correction. A further feedback loop responsive to the active filter output signal and normally open under steady-state conditions, is closed under transient conditions for supplying a limited gain reducing signal to the input of the active filter whereby transient disturbance of the primary and nested loops is minimized with no loss of loop gain under steady-state conditions. The third loop includes a dead zone amplifier for distinguishing between transient and steady-state conditions and a limiter for limiting the gain reducing signal to a level below that which otherwise would tend to drive the active filter into a non-linear slow recovery condition.</p> |
