RECORDING AND REPRODUCING CIRCUIT FOR MAGNETIC HEAD

PURPOSE:To improve an SN by using a field effect transistor (FET) having high reverse dielectric strength to form a reproducing preamplifier. CONSTITUTION:Since a writing gate signal inputted from a terminal 17 is turned to a low level and a transistor (TR) 15 is disconnected at the time of reproducing, a TR 16 operates as a constant current circuit. Thereby, differential amplifiers consisting of FETs 11, 12 and 13, 14 respectively are turned to operatable states. On the other hand, a control voltage for selecting a head is inputted to any one of input terminals 3, 4 similarly to the recording case. The control voltage provides operating biases to the FETs 11-14 unlike the recording case. At the time of reproducing, both of constant current circuits respectively connected to input terminals 5, 6 are turned to non-operating state with high impedance and practically disconnected from the terminals 5, 6.