| 摘要 |
<p>A clipper circuit (32) is disclosed which prevents an input signal level from going beyond a predetermined minimum (or maximum) level. The clipper circuit (32) has at least three terminals: a input terminal (36), an output terminal (38), and a reference terminal (40). It includes an impedance, such as a resistor (46), connected between the input and output terminals (36, 38), and a transistor (48). The base of the transistor (48) is connected to the input terminal (36), and the collector-emitter current path of the transistor (48) is connected between the output terminal (38) and the reference terminal (40). A reference potential (e.g., ground potential) representing the desired clipping level is applied to the reference terminal (40). When the input signal level is on one side of the reference potential, the transistor (48) is cut off and thus the input signal is transmitted to the output terminal (38) without change. When the input signal tends towards the other side of the reference potential, however, the transistor (48) turns on and saturates, thereby preventing the output signal from exceeding the reference potential. A zero crossing detector is disclosed which uses the clipper circuit (32) to protect the input of a comparator circuit which is operated from a single-voltage power supply.</p> |
