| 摘要 |
PURPOSE:To obtain a stable reproduced picture at the time of high speed reproduction by providing a gain and phase compensating circuit with the characteristics of a low-pass filter and preventing the increment of gain at a high frequency area under the control of a rotating body such as a capstan motor for a VTR device. CONSTITUTION:A signal (ei) obtained by mixing a speed signal with a phase signal of the capstan motor is inputted to a positive input terminal 21 of an operating amplifier 22 (amplification factor An) and the output signal eo of the amplifier 22 is impressed to a negative input terminal of the operating amplifier 22 through a voltage devider 23 (voltage deviding ratio beta) and a resistor R in series. The transmission function EN of the circuit is expressed by the formula I , and if An infinity , eo/ei is expressed by the formula II. The amplification factor in a low frequency area is eo/ei=1/beta in case of S 0 and that in a high frequency area is eo/ei=1 in case of S infinity . Consequently, the transmission function of one cycle of a speed system is compensated by changing the voltage dividing ratio of the voltage divider 23 to switch the gain in the low frequency area, and in the high frequency area, the gain is turned to ''1'' and a carrier frequency component is not amplified. |
