Operational amplifier

Abstract

An operational amplifier includes a differential amplifier input stage that supplies an operating current to a differential pair, the differential amplifier input stage including a first transistor having a first polarity, a push-pull amplifier output stage that includes a second transistor having the first polarity, and a third transistor having a second polarity, the second transistor and the third transistor being connected in series, a first capacitive element that connects a gate of the first transistor and a gate of the second transistor, and a second capacitive element that connects the gate and a drain of the first transistor.

1 . An operational amplifier comprising:
 a differential amplifier input stage that supplies an operating current to a differential pair, the differential amplifier input stage comprising a first transistor having a first polarity;   a push-pull amplifier output stage that comprises:
 a second transistor having the first polarity; and 
 a third transistor having a second polarity, the second transistor and the third transistor being connected in series: 
   a first capacitive element that connects a gate of the first transistor and a gate of the second transistor; and   a second capacitive element that connects the gate and a drain of the first transistor.   
     
     
         2 . An operational amplifier comprising:
 a differential amplifier input stage that supplies an operating current to a differential pair, the differential amplifier input stage comprising a first transistor:   a push-pull amplifier output stage that comprises:
 a second transistor; and 
 a third transistor connected in series with the second transistor, the second transistor and the third transistor having different polarities; 
   a first capacitive element that connects a gate of the first transistor and a gate of anyone of the second transistor and the third transistor; and   a second capacitive element that connects the gate and a drain of the first transistor,   wherein a first potential, which varies inversely with a second potential of an input signal input to the differential amplifier input stage, is supplied to a terminal of the first capacitive element that is connected to the gate of either the second transistor or the third transistor.   
     
     
         3 . The operational amplifier according to  claim 2 , wherein a transistor that is connected to the gate of the first transistor through the first capacitive element has a same polarity as that of the first transistor. 
     
     
         4 . The operational amplifier according to  claim 1 , wherein the push-pull amplifier output stage further comprises a level shift circuit that outputs a differential output voltage after level-shifting the differential output voltage, and the push-pull amplifier output stage is driven based on the differential output voltage and the level-shifted voltage. 
     
     
         5 . Hie operational amplifier according to  claim 1 , wherein the differential pair comprises P channel MOS transistors, the first and the second transistors each comprise a P channel MOS transistor, and the third transistor comprises an N channel MOS transistor, and
 a negative potential is supplied from the gate of the second transistor to the gate of the first transistor when an output signal from the differential amplifier input stage is raised.   
     
     
         6 . The operational amplifier according to  claim 1 , wherein the differential pair comprises N channel MOS transistors, the first and the second transistors each comprise a N channel MOS transistor, and the third transistor comprises a P channel MOS transistor, and
 a positive potential is supplied from the gate of the second transistor to the gate of the first transistor when an output signal from the differential amplifier input stage is fallen.