| 摘要 |
PURPOSE:To simplify circuit constitution and to reduce noises by using an MR (Magnetoresistive) head as part of the feedback circuit of a regenerative amplifying circuit since the MR head is a resistance. CONSTITUTION:When the gain of the opened loop of a differential amplifying circuit 7 is much greater than that of the closed loop, a current is supplied to an MR head 5 through a resistance so that a voltage at a connection point between the resistance 23 and MR head 5 is equalized to that at a connection point between resistances 21 and 22. If the MR head 5 varies in resistance by an external magnetic field applied to the MR head 5, an output voltage proportional to the resistance variation of the MR head 5 is developed across the resistance 23. Further, only the resistance noise of the MR head 5 and the transistor noise of the circuit 7 are left as noise sources. Therefore, circuit constitution is simplified and noises are reduced with the constitution like this. |
