| 摘要 |
PURPOSE:To realize the demodulation circuit with high performance, by using an inverse amplifier and a switching means to eliminate defects such as the increase in a distortion factor, the reduction in a dynamic range and the provision of a muting circuit. CONSTITUTION:When a subcarrier is at high level at the receiving of a stereo signal, switches G1, G2 are turned on and switches G3, G4 are turned off, and a composite signal is amplified inversely by an operational amplifier OP1 and outputted to be L channel information during this period. The amplifier gain of the amplifier OP1 in this case goes to 2R6/R(R=R1=R2). When the subcarrier is at low level similarly, the output of an operational amplifier OP2 represents R channel information, the gain goes to 2R6/R(R=R3=R4), and when R5=R6, the L, R channel signals are of the same level, allowing to adjust the separation of left and right channels. At the monaural signal receiving, the output is at the same output level as the stereo operation, and at muting, a low level muting signal E is applied to switches G1-G5, the transmission to a signal output section is interrupted, allowing to attain muting. |
