| 摘要 |
PURPOSE:To shorten the distance from a video head to an amplifier circuit and to prevent the influence of noises by blowing a recording signal and a reproducing signal into a video head circuit without using a switching element. CONSTITUTION:At the recording, a recording signal impressed to an input terminal 4 is amplified and outputted by/from a recording amplifier circuit 1. The impedance of the video head 2 for the output recording signal is normally <=100OMEGA, but the input terminal of a reproducing amplifier circuit 3 is high impedance because the input terminal consists of an emitter, a follower, etc. Since the input terminal 4 is opened at the reproducing, the output current of the recording amplifier circuit is about ''0''. The bark current of the output of the recording amplifier circuit 1 is sufficiently low current of generally about 1mA, and if the impedance of the video head 2 is 100OMEGA, the current flowing into the video head 2 is several muV or less when considering voltage drop, and the current value can be ignored as compared to the several hundred muV, the voltage level of the reproducing signal. As compared to the input terminal of the reproducing amplifier circuit 3, the output terminal of the recording amplifier circuit 1 has sufficiently high impedance. Therefore, the reproducing signal detected by the video head 2 is impressed to the reproducing amplifier circuit 3. |
