Patent ID: 7385450

Claim:
A bias circuit comprising: a connection point adapted to receive an alternating current signal; a first reactance means one end of which is connected to said connection point; a capacitive means one end of which is connected to the other end of said first reactance means and the other end of which is connected to ground, and a direct current circuit supplying a DC voltage to the connection between said first reactance means and said capacitive means; a second reactance means one end of which is connected to said connection point at the one end of said first reactance means; and a regulating means for regulating the reactance value of at least one of said first reactance means, said second reactance means, and said capacitive means, wherein the respective reactance values on the side of said first reactance means and said second reactance means, and of said capacitive means, are set so that the total admittance, seen from the connection point of said first reactance means and said second reactance means, becomes zero and the connection point is connected to supply the received alternating current signal and a received bias voltage to a radio frequency amplifying element.