| 摘要 |
PURPOSE:To realize the increment of the gain control range as well as enhancement of the cross modulation property by connecting the signal attenuator using the PIN diode to the input side of the FET forming the amplifier circuit and then controlling the attenuator with the source current of the PIN diode FET. CONSTITUTION:The PIN diode signal attenuator is connected to input terminal G1 of FET1, and PIN diode 13 and 12 are controlley by the source current of FET1. At the same time, resistance 14 and 17 of the signal attenuator are used as the source resistance of FET1. In such constitution, diode 3 changes from the conducting state to the breaking state by reduction of the drain current which is caused by reduction of the gain control voltage applied to control terminal 3. On the other hand, diode 12 changes from the breaking state to the conducting state as the potential of point A reduces, thus attenuating the signals applied to gate G1. In this way, the cross modulation property can be improved greatly along with increment of the gain control amount as shown in the diagram. |
