| 摘要 |
PURPOSE:To reduce an output of a main amplifier even if an excessive input is applied to a differential amplifier of a pre-stage by turning off a switch inserted in series in an input line of the main amplifier, when an instant switch is turned on. CONSTITUTION:When an electrocardiogram signal is fluctuated suddenly by an artifact such as a body motion, etc., of a testee, the electrocardiogram signal does not return to a base line level potential in a short time due to a large time constant of a primary filter constituted of an AC coupling capacitor 3 and a resistor 6. Therefore, an instant switch 4 is turned on, and charge charged to the capacitor 3 is discharged. In the case a high level signal which cannot be attenuated even by a resistor 2 and turn-on resistance of the switch 4 is inputted, a second d switch 5 is inserted in series in an input line of a amplifier 7 in order to suppress an input of the main amplifier 7 to the minimum. In such a way, when the switch 4 is turned on, a switch 5 is turned off by an inverter 8. |
