| 摘要 |
<p>PURPOSE:To omit a transistor consuming a large quantity of electric power, a heat dissipation fan, etc. by providing a feed circuit which has a high impedance to the differential AC signal produced between both channels and then a low impedance to the in-phase AC signal respectively. CONSTITUTION:The resistance is controlled so as to obtain the same DC potential between input terminals of operational amplifiers 101 and 102 respectively. Then an output current is set at 0. The capacities of capacitors 108 and 208 are increased enough and therefore both amplifiers 101 and 201 function as a differential amplifier circuit having the 1/2 gain to the AC signals supplied from channels (a) and (b). Thus the AC output potential of the amplifier 101 is equal to the AC potential of the channel (b) together with the AC output potential of the amplifier 201 set equal to the AC potential of the channel (a) respectively in case the differential AC signals of sound signals, etc. are produced on the channels (a) and (b). While the AC potentials of amplifiers 101 and 201 are equal to the ground potential to produce a low impedance in case the in-phase AC signals are produced on both channels.</p> |
