Electric field intensity detecting circuit and limiter amplifier

摘要

A second differential amplifier (12) is additionally disposed in parallel with at least a part of first differential amplifiers (11) in respect to a differential amplifying circuit comprising a multi-stage connection of the first differential amplifiers (11) so that a to-be-detected signal may be obtained from the second differential amplifier (12) via a transistor (Qi). Thus, a large current is made to flow through a constant current circuit (Ii1) which constitutes the first differential amplifier (11) to increase a differential amplification gain. A small current is made to flow through a constant current circuit (Ii2) which constitutes the second differential amplifier (12), thereby increasing the signal level for detection.