| 摘要 |
PURPOSE:To suppress an increase in the noise index of a wide-band amplifying circuit consisting of a variable attenuator and an amplifying circuit, by using the amplifying circuit which uses a PIN diode as a feedback circuit. CONSTITUTION:An amplifying circuit 23 is provided with a current feedback circuit 8 and a voltage feedback circuit which uses a PIN diode 7. Thus, a wide- band amplifying circuit consists of this amplifying circuit 23 and a variable attenuator 2; and AGC is exercised at the terminal 22 of the amplifying circuit 23, and then AGC over the variable attenuator 2 is performed. Consequently, an increase in noise index is suppressed more than that by the AGC over only the variable attenuator 2. Further, the same effect is obtained even when the current feedback circuit 8 uses the PIN diode. |
