| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a bias circuit capable of suppressing variation in bias voltage even when a gate current greatly varies as the operation state of a transistor changes between saturated operation and unsaturated operation, to provide an amplifier circuit equipped with the bias circuit, and to provide a communication device. <P>SOLUTION: A transistor Q1 is connected between an output node N1 which outputs a bias voltage and a voltage supply line VDD and a transistor Q2 controls the gate voltage of the transistor Q1 to suppress variation in bias voltage corresponding to variation of a current outputted from the output node N1. Consequently, even when a signal with a large amplitude which causes the operation state of the transistor Qamp to change between the unsaturated operation and saturated operation is inputted to an input terminal Tin to cause the gate current of the transistor Qamp to greatly vary, the transistor Tamp can be made to operate at a desired bias point. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
