LOW FREQUENCY SIGNAL CIRCUIT

摘要

PURPOSE:To decrease noise at an input side of an amplifier by providing a means decreasing the input impedance of the low frequency amplifier when an analog switch intermitting a low frequency signal is turned off to an output side of the analog switch. CONSTITUTION:The low frequency signal inputted from an input terminal 4 is led to the analog switch 1 through a buffer amplifier 2. The switch 1 is turned on/off by a control signal inputted from a control signal terminal 5. The low frequency signal is amplified by the low frequency amplifier 3 at turning-on and lef out of an output terminal 6. A capacitor 12 decreases a signal source impedance of the amplifier 3 when the switch 1 is turned off so as to prevent a noise signal from being induced.