| 摘要 |
PROBLEM TO BE SOLVED: To provide a differential amplifier that reconciles a high frequency signal amplification and a variable common mode rejection ratio.SOLUTION: The differential amplifier includes: an amplification section with a variable gain; a differential amplification section cascade-connected to the amplification section; a detection section for detecting an output amplitude of the differential amplification section; and a change section for changing the gain of the amplification section in accordance with the detection result of the detection section. The differential amplification section has a common source amplification section, and a source follower amplification section having a plurality of N channel field effect transistors for performing an amplification operation with the common source amplification section, and capable of reducing a common mode gain in the amplification operation. In the source follower amplification section, the N channel field effect transistors can be at least partly set on or off. |
