Patent ID: 6456108
Filing Date: 2002-09-24
Classification: H03K

Abstract:
An input circuit for an output stage for suppressing electrical interference and electromagnetic interference in a control signal, comprising:a signal input connected to a signal line carrying the control signal; a signal output connected to the output stage; a ground terminal; a first switch stage including a first control terminal, a first signal terminal, and a first output terminal, the first switch stage further including a first resistor, a first transistor, and a third transistor, the first resistor being connected between a collector of the first transistor and the first signal terminal, an emitter of the first transistor being connected to ground, a base of the third transistor forming the first control terminal of the first switch stage, and an emitter of the third transistor controlling a base of the first transistor; a voltage divider, wherein: the first control terminal is connected to the voltage divider between a potential at the signal input and the ground terminal, and the first signal terminal is connected to the signal line; and a second switch stage including a second control terminal, a second signal terminal, and a second output terminal, the second switch stage further including a second resistor and a second transistor, the second resistor being connected between a collector of the second transistor and the second signal terminal, and an emitter of the second transistor being connected to ground, wherein: the second control terminal is connected to the first output terminal of the first switch stage, the second signal terminal is connected to the signal line, the second output terminal is connected to the signal output, when a first threshold value is exceeded, the first switch stage switches over from a first state in which a potential at the first output terminal follows the potential at the signal input to a second state in which the potential at the first output terminal is drawn to ground, when a second threshold value is exceeded, the second switch stage switches over from the first state in which a potential at the second output terminal follows the potential at the signal input to the second state in which the potential at the second output terminal is drawn to ground, and the first threshold value is higher than the second threshold value.