| 摘要 |
PURPOSE:To control two different negative control voltages with one positive fixed power source and one other positive control power source by connecting a circuit composed of plural resistances to the gate source of respective FETs or a drain. CONSTITUTION:The division between respective gate electrodes of respective FETs 101-103 of a pi type coupling is connected with plural resistances 104-110. To an attenuation quantity control terminal 112, the voltage higher than a constant voltage impressing terminal 113 is impressed. Since the resistances 104 are connected to the gate of the FET 101, a current hardly flows. The FET101 is completely in an on condition and the FETs 102 and 103 are in the condition having a resistance value in accordance with a gate bias. As the potential of the terminal 112 is lowered, the condition is close to the inversion, and when the potential of the terminal 112 is lower than the potential of a node point 118, the condition is completely inverted. The resistance value of the FET101 is freely controlled by the terminal 112.
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