CURRENT SWITCHING CIRCUIT AND RECORDING/REPRODUCING AMPLIFIER USING THE SAME

PROBLEM TO BE SOLVED: To provide a current switching circuit which is so contrived so that a write voltage generated between head connecting terminals during the recording operation is determined only by a circuit constant independently of the power supply voltage and a recording/ reproducing amplifier of which the transistors are not broken down or which is not restricted in its power supply voltage due to such breakdown by incorporating such a current switching circuit therein. SOLUTION: This recording/reproducing amplifier 1 has a current switching circuit (for example, differential transistor pair of a recording amplifier 2) for controlling the direction of a write current to be supplied to a magnetic recording head depending on an input signal SG. Moreover, when one potential of the voltage between terminals Th1, Th2 changes depending on the power supply voltage, a circuit for eliminating the element depending on the power supply voltage from the relevant terminal voltage by generating the other potential with reference to the power supply voltage is also provided. This circuit is connected between the head connecting terminals (between points E and F) and comprises stopper transistors Q14, Q20 for restricting the lower limit of the relevant potential and a stopper bias setting circuit 6a for holding its control input terminal with the constant voltage generated with reference to the power supply voltage.