Logarithmic/inverse-logarithmic conversion circuit

摘要

A logarithmic conversion circuit comprises: an operation amplifier; an input resistor connected at a preceding stage of an inverting input terminal, of the operation amplifier, to which a current signal is inputted; and a logarithmic conversion device and a current feedback device connected in series between the inverting input terminal and an output terminal of the operation amplifier, and an inverse-logarithmic conversion circuit comprises: a current/voltage conversion circuit which, after the current signal having passed through the current feedback device is inputted, converts the inputted current signal to a voltage value corresponding thereto; and a subtraction circuit outputting the difference between an output voltage of the current/voltage conversion circuit and a predetermined reference voltage, a circuit constant of the subtraction circuit being set such that the difference output of the subtraction circuit has a linearity proportional to the current signal.

主权项

1. A logarithmic/inverse-logarithmic conversion circuit comprising:
a logarithmic conversion circuit which performs logarithmic conversion for an inputted current signal and outputs a logarithmic converted current signal; and an inverse-logarithmic conversion circuit which performs inverse-logarithmic conversion for the logarithmic converted current signal that has passed through the logarithmic conversion circuit and outputs a resultant current signal, wherein the logarithmic conversion circuit comprises: an operation amplifier; an input resistor connected to an inverting input terminal of the operation amplifier, to which the current signal is inputted; and a logarithmic conversion device and a current feedback device connected in series between the inverting input terminal and an output terminal of the operation amplifier, the inverse-logarithmic conversion circuit comprises: a current/voltage conversion circuit to which the logarithmic converted current signal that has passed through the current feedback device is inputted and which converts the logarithmic converted current signal to a voltage value corresponding to the logarithmic converted current signal; and a subtraction circuit which outputs the difference between an output voltage of the current/voltage conversion circuit and a predetermined reference voltage, and a circuit constant of the subtraction circuit is set such that the difference output of the subtraction circuit has a linearity proportional to the inputted current signal.