| 摘要 |
A differential amplifier formed of MISFETs includes a differential amplification stage and a pair of cascade amplification stages which receive outputs from the differential amplification stage. In each of the cascade amplification stages, an amplifying MISFET which receives an input signal at its source has a channel conductivity of opposite type to that of the differential input MISFETs of the differential amplification stage. The differential amplifier with this construction has good frequency characteristics. Since the pair of cascade amplification stages make the currents taken from a pair of outputs from the differential amplification stage equal to each other, the operating balance of the differential amplification stage is not affected. The differential amplifier further includes a feedback circuit which detects the operating points of these cascade amplification stages by referring to the outputs of the cascade amplification stages, and generates a control voltage by comparing the operating points thus detected with a reference potential. The control voltage is fed back to the gates of the amplifying MISFETs in each cascade amplification stage. As a result, the operating point of each cascade amplification stage can be stabilized irrespective of variations in the characteristics of the MISFETs or the changes of their characteristics.
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