| 摘要 |
<p>A digital servo circuit which, for example, may be used in a video tape recorder, for controlling the velocity and the phase of movement of a video tape by a capstan which is driven by an electric motor. The circuit includes a frequency generator for generating a pulse signal having a repetition rate that varies in accordance with the velocity of the capstan, and hence of the tape driven thereby an n-bit presettable counter for counting a reference clock signal during an interval corresponding to the repetition rate of the pulse signal, a latch circuit for latching the least significant m output bits of the counter (where m is less than n), a control circuit for controlling the m-bit output from the latch circuit so as substantially to hold the latter output at the minimum level when the n-bit output from the counter is less than a first predetermined value, and at the maximum level when the n-bit output from the counter is more than a second predetermined value, and a digital-to-analog converter for converting the m-bit output from the latch circuit to the corresponding analog signal to drive the motor.</p> |
