| 摘要 |
A variable resistance circuit includes a PIN diode circuit which adjusts an RF resistance for PIN diodes according to a control voltage, a first means which level-shifts one control voltage by a level shift circuit and applies a non-linear characteristic to the so level-shifted control voltage using a zener diode characteristic by a zener diode circuit, a second means which applies a voltage offset to the other control voltage by a weighting circuit, and an adding circuit which adds respective output voltages of the first means and the second means. When the output of the adding circuit is applied to the PIN diode circuit, the shift voltage of the level shift circuit, the zener characteristic of the zener diode circuit and the voltage offset of the weighting circuit are selected and adjusted to set the value of the RF resistance of the PIN diode circuit so as to change substantially linearly with respect to a change in control voltage.
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