| 摘要 |
PURPOSE:To reduce effect due to fluctuation of polarized voltage by feeding back an output voltage of a low-pass filter circuit taking an output voltage of an amplifier circuit as an input signal to an inverting input of the amplifier circuit so as to decrease the gain from an ultra low frequency to a DC band in the frequency characteristic of the entire amplifier circuit. CONSTITUTION:A low-pass filter 32 leading an output signal to a capacitor from an output terminal 30 of a cardiograph amplifier circuit via a resistor 31 and receiving the signal at a buffer 33 of a high input impedance and a signal line 36 feeding back an output of the low-pass filter to an inverting input terminal 35 as the entire cardiograph amplifier are connected to the amplifier consisting of resitors 26, 27, 28 connected to a differential amplifier 10 inputting an output signal of operational amplifiers 5, 6 and an operational amlifier 29. Only a low frequency component being the cut-off frequency or below decided by the time constant of the low-pass filter comprising a resistor 31 and a capacitor 32 among signals outputted to an output terminal 30 is applied to a non-inverting input 41 of the operational amplifier 33. Furthermore, the output of the low-pass filter is connected to an inverting input terminal 35 as the entire cardiograph amplifier circuit via a bias resistor 40. |
