| 摘要 |
PURPOSE:To obtain stable operation and enhance accoustic quality of a tape recorder by providing a feed back circuit wherein a medium running speed is defined as a reference speed and a comparating frequincy is constant for both high- and low- motor speed. CONSTITUTION:A reference frequency otained by a reference-frequency generator SF and a comparating frequency obtained by a comparating-frequency setting circuit CFS are compared in a phase comparator PC, and output pulses which correspond to the phase difference are generated. An LPF converts the output from the comparator PC to a direct current, sends it to a driving amplifier A1, and rorates an ac motor ACM. While, a rotation sensor FG, which is moved with the motor, converts the number of rotation to pulses, and sends them to an amplifier A2, to a wave- form shaping circuit SH, and to the comparating-frequency setting circuit CFS, where the pulses are converted to a comparating frequency which corresponds to the position of a speed-setting unit SW, thereby stable operation can be obtained. |
