| 摘要 |
PURPOSE:To reduce the disorder of an output due to the disorder of load impedance by using an output, obtained by expanding and controlling the instantaneous value of an output voltage by the absolute value of a current flowing through the voice coil of a speaker, as a negative feedback signal to an power amplifier. CONSTITUTION:An input signal Vs is inputted to a power amplifier A and while an amplified output current Io is supplied to the voice coil VC of a speaker SP as a load, an output voltage Vo is inputted to an expanding circuit Me constituting a multiplying circuit M. To the other input of the circuit Me, an output obtained by making the voltage Vi of a small resistance Ri for current detection provided in series to the coil VC into an absolute vlue by an absolute value circuit Md is applied. The output Vf of the circuit Me, obtained by expanding and controlling the instantaneous value of the output voltage Vo by the absolute value signal of the output current Io is fed back to the amplifier A. This constitution reduces the disorder of the output due to the disorder of load impedance to perform sound reproduction with stable and composure quality. |
