| 摘要 |
PURPOSE: To accurately detect strength of a received signal by using a current source, having a temperature characteristic different from that of another current source for biasing an amplifier section, thereby biasing a detection section. CONSTITUTION: Output from an amplitude detection section 21 is practically unchanged, even when an absolute temperature is subjected to change so long as the strength of a received signal is constant. When using a constant current source without temperature dependence for a current source 40 to bias the amplitude detection section 21, a collector current Ic outputted from differential amplifiers 23-25 is unchanged, even if the absolute temperature changes as long as the strength of the received signal remains constant. Since a constant current source, whose characteristic is proportional to the absolute temperature T, is used for a current source 12 biasing a logarithmic amplifier section 1 and a constant current source whose characteristic is not proportional to the absolute temperature T is used for the current source 40 biasing the amplitude detection section 21, the detector is immune to the temperature change.
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