| 摘要 |
PURPOSE:To prevent an input transistor (TR) from deteriorating and damaging owing to a large input signal during writing operation by applying a bias current from a current source which becomes active during reading operation to the connection point of a differential amplifier constituted by cascading two states of input TRs of a disk type magnetic recording device. CONSTITUTION:Input TRs Q1 and Q3, and Q2 and Q4 of the differential amplifier of a read amplifier circuit are cascaded in two stages to increase the emitter- base dielectric strength twice. The 1st controllable current source ICC1 which supplies a bias current to the amplifier circuit and bases of TRs Q5, Q6, and Q7 as current sources supplying bias currents to cascade connection point associatively with the current source ICC1 are connected to the base-collector connetion line of the TRQ8. Further, A read and write amplifier is equipped with a centertap type magnetic coil L which supplies complementary inputs to input terminals of the amplifier, write TRs Q9 and Q10 which switch the coil 1 complementarily, and the 2nd controllable current source ICC2 connected to emitters of the Q9 and Q10 in common. Consequently, the amplifier withstands a large signal voltage in writing operation. |
