Patent ID: 7430103

Claim:
A static electricity protective circuit for use in a high-frequency apparatus for protecting, against static electricity, an internal circuit connected to a signal terminal through which a high-frequency signal that is transmitted from the internal circuit of the high-frequency apparatus to outside and a DC (Direct Current) signal are superimposed and transmitted, the DC signal being provided to the signal terminal from an external device as a power source for driving the high-frequency apparatus, comprising: a high-frequency cut-off element having a first end thereof connected to a node between the signal terminal and a first end of a DC current cut-off capacitor having a second end thereof connected to the internal circuit to cut off the DC signal, the high-frequency signal and the DC signal being applied to the high-frequency cut-off element through the node; and a Schottky barrier diode having a cathode thereof connected to a second end of the high-frequency cut-off element and an anode thereof connected to ground, wherein the DC signal is applied to the first end of the high-frequency cut-off element through the signal terminal and flows into the internal circuit through another circuit by bypassing the high-frequency cut-off element, the high-frequency cut-off element cuts off the high-frequency signal which is applied to said first end of the high-frequency cut-off element, the Schottky barrier diode has a reverse voltage characteristic thereof that causes the DC signal which has been applied to said first end of the high-frequency cut-off element to be cut off so as not to flow through the high-frequency cut-off element, and the high-frequency cut-off element and the Schottky barrier diode together lead static electricity applied to the signal terminal to ground so as to protect the internal circuit against the static electricity.