| 摘要 |
PURPOSE:To obtain a steep limiter characteristic by detecting a gate leakage current of an output amplifier element and controlling the attenuation of a variable attenuator in response to the detected value so as to keep the input power to an amplifier of the output stage to a constant value. CONSTITUTION:The gate leakage current of an FET51 used for the output stage of the amplifier 1 is detected and the attenuation of the variable attenuator 2 is controlled depending on the detected current in a control circuit 5. The gate leakage current of the FET51 being the amplifier element of the output stage amplifier 4 is detected and used for an input signal of the control circuit 5 to control the said attenuation in response to the detection current. When the gate leakage current exceeds a prescribed value, a control signal is fed to the variable attenuator 2 in the range thereover to control so that the attenuation is increased thereby making the output level of the variable attenuator 2 constant. |
