| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a detective logarithmic amplifier that has satisfactory linearity over a wide band and a wide dynamic range by controlling the operating point of a logarithmic amplifier by means of a variable attenuator. <P>SOLUTION: The detective logarithmic amplifier includes: the variable attenuator having an attenuation continuously variable with an external control voltage; an amplifier connected to an output of the variable attenuator; a detector connected to an output of the amplifier to generate a DC detection output depending on input signal power; the logarithmic amplifier connected to the output of the detector; a controller having the function of outputting a control signal to increase the attenuation of the variable attenuator when an output voltage of the logarithmic amplifier is higher than a first reference voltage and outputting a control signal to decrease the attenuation of the variable attenuator when the output voltage of the logarithmic amplifier is lower than a second reference voltage; a conversion circuit for outputting a predetermined multiple of the control voltage to the variable attenuator; and an adder for adding up the output of the logarithmic amplifier and the output of the conversion circuit. <P>COPYRIGHT: (C)2013,JPO&INPIT |
