| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that, if an output voltage amplification circuit of a folded cascode operational amplifier comprises bipolar transistors, an input current to the bipolar transistors causes an amplification factor drop and a noise increase.SOLUTION: A circuit 200 comprising a two-stage emitter follower circuit and a ground capacitance is disposed between a folded cascode amplification circuit 100 and an output voltage amplification circuit 300 comprising bipolar transistors. The two-stage emitter follower circuit is configured to amplify a current, which is small in the front stage and large in the rear stage. The reduction in the current drawn by the emitter follower circuit from an output section A of the folded cascode amplification circuit 100 suppresses an output resistance drop of the folded cascode amplification circuit 100 to maintain an amplification factor, and reduces output noise due to a noise component in the current drawn. As for white noise caused by the current reducing emitter follower having a small current, a high frequency component is removed in a low pass filter comprising the emitter follower and the ground capacitance. |
