| 摘要 |
PURPOSE:To detect an abnormality such as disconnection of a magnetic head, etc. without deteriorating the performance of a writing circuit and without causing a malfunction, by detecting the disconnection of the magnetic head or a fact that a current of a current supply means becomes zero substantially by on and off of a current from a detection terminal. CONSTITUTION:When a voltage of a head terminal 122 in case a magnetic head is disconnected is denoted as -VL, and values of a resistance 118 and 123 are determined so as to become a relation as shown in an expression, currents of a transistor 106 and 112 become zero when the magnetic head is disconnected, and accordingly, a current of a terminal 111 becomes zero, therefore, a disconnection of the magnetic head can be detected. Also, even in case a current of a constant-current source 110 becomes zero, the current of the terminal 111 becomes zero, therefore, a fault by which a write current becomes zero at the time of write can also be detected. As for this circuit, even in case a voltage difference of a head terminal 121 between the normal time and the time when the magnetic head is disconnected in small, the current of the terminal 111 becomes zero, when the magnetic head is disconnected, and at the normal time, a current determined by transistor parameters of the transistor 106 and 112 flows, therefore, an abnormality is detected easily. |
