LIMITER CIRCUIT

PROBLEM TO BE SOLVED: To provide a limiter circuit which realizes low passing loss when a small-signal is inputted and sets a passing power level when a large-signal is inputted. SOLUTION: A power detecting circuit 6 extracts a part of power of a high-frequency signal inputted to a transmission line 3 from an input terminal 1, and a wave detector 7 detects the voltage corresponding to the extracted power. A comparator 8 compares the reference voltage Vref, set in advance, with a detected voltage Vdet by the wave detector 7, generates an output voltage Vcom, set in advance, when the detected voltage Vdet is higher than the reference voltage Vref, applies the voltage Vcom to an output portion of a PIN diode 5 as bias voltage, and stops generation of the outputted voltage Vcom, when the detected voltage Vdet is lower than the reference voltage Vref. The bias voltage is not applied to the PIN diode 5 when the small-signal is inputted, low passing loss is realized, rapid passing power restriction is conducted by applying the bias voltage to the PIN diode 5 when the big-signal is inputted, and the passing power level is set. COPYRIGHT: (C)2005,JPO&NCIPI