| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a new radio frequency signal receiving head which is assigned to a dual band system by using only a signal low noise amplifier. SOLUTION: This amplifier circuit includes at least one 1st input amplifier T1, at least one 2nd amplifier T3 cascaded with the 1st amplifier and at least one invalid impedance circuit which includes two impedances Z1 and Z2 respectively showing a maximum value to 1st and 2nd frequencies f1 and f2 to form a dual band amplifier circuit and is serially attached to the 2nd amplifier. The impedances Z1 and Z2 are serially connected and made to be a size so as to respectively show the maximum value and high acutance by one of the two operation frequencies f1 and f2.</p> |
