| 摘要 |
PURPOSE:To obtain the gain difference between both the systems by using a couple of feedback type operational amplifier circuits so as to change over the two-amplifier system driving independent loads and the BTL system giving high ouptut amplification. CONSTITUTION:In throwing contacts of switches S1-1, S1-2 to the position L, an inverting input terminal of the feedback type operational amplifier circuit 20 is connected to ground via a resistor R22, a signal inputted to a non-inverting input terminal of the feedback type operational amplifier circuit 10 is inputted to the non-inverting input terminal of the circuit 20 to constitute the connection of the two amplifier system and the gain of the circuits 10, 20 is expressed as (R11+R12)/R12. In throwing the contacts to the position H, an output of the circuit 10 is inputted to the inverting input terminal of the circuit 20 via resistors R11, R12 and R22(R221+R222), the non-inverting input terminal is connected to ground to constitute the connection of the balanced transformerless (BTL) system, and a prescribed increased gain is obtained by halving the resistance between the inverting inputs of the circuits 10, 20. Thus, the gain difference between the BTL system and the two-amplifier system is obtained.
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