| 摘要 |
A motor speed control circuit, for example, for the turntable drive motor of a phonograph record player, is of the type having a phase-locked loop including a frequencydivider with a dividing ratio which is changeable for altering the rotational speed of the motor, for example, so as to selectively establish turntable speeds of 45 rpm and 33 1/3 rpm, and has the gain of one of the components of the phaselocked loop, such as, the servo-amplifier, the loop filter or the phase comparator, varied in accordance with changes in the dividing ratio of the frequency-divider so that the loop gain of the phase-locked loop is maintained substantially constant regardless of the rotational speed of the motor. |
