| 摘要 |
PROBLEM TO BE SOLVED: To provide a signal amplifier in which a music tone signal is attenuated without causing incongruity in the case of limiter operation. SOLUTION: A 1st amplifier 22 monitors whether or not an output voltage V0 exceeds a threshold voltage Th1 positively and when exceeded, the 1st amplifier 22 generates a detection voltage V1 in response to a degree of the excess. A 2nd amplifier 24 monitors whether or not the output voltage V0 exceeds a threshold voltage Vth2 negatively and generates a detection voltage v2 of the same polarity as that of the detection voltage V1 and in response to the degree of the excess when exceeded. An OR circuit 26 ORs the detection voltages V1, V2 and outputs a detection voltage Vs being the result of arithmetic operation. A time constant circuit 18 processes the detection voltage Vs so that the absolute value of a time change rate of the detection voltage Vs is reduced and generates a control voltage Vc. A variable impedance circuit 20 attenuates an input signal depending on the control voltage Vc. |
