Operational amplifier adopted for input and output in wide ranges for driving a large load

摘要

An operational amplifier comprises an input stage, an output stage, and an intermediate circuitry connected between the input stage and the output stage. The operational amplifier may be biased between a high voltage line and a low voltage line. The input stage includes at least an amplifier circuit. The intermediate circuitry comprises at least a first pair of a first transistor and a first constant current source, both of which are connected in series to each other between the high voltage line and the low voltage line. The first pair may be adjacent to the output stage. A first intermediate point between the first transistor and the first constant current source may be connected to the output stage. At least a second pair of a second transistor and a second constant current source is provided, both of which are connected in series to each other between the high voltage line and the low voltage line. The second pair may be in parallel to the first pair and may be adjacent to the input stage. A second intermediate point between the second transistor and the second constant current source may be connected to a control electrode of the first transistor the output stage. A control gate of the second transistor may be connected to the input stage.