Importance

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Abstract

An operational amplifier (10a) comprised of MOSFET elements is disclosed which provides for a variable drive for an output stage that results in lower power dissipation and increased gain factor over comparable circuits using constant bias drive for the output stage. A bias section (14) comprised of complementary MOS elements (24, 26) is connected to a single MOSFET (40) that furnishes constant current to the signal input section of a differential amplifier section (20). The output of this differential amplifier is furnished by one path (70) directly to one complementary MOSFET element (72) of an output stage (18) and by another path (114) to a level shift section (16) which provides an output to a second complementary MOSFET element (80) of the output stage. Thus, the circuit functions under class A-B operation at low power dissipation and provides high open loop gain. This invention utilizes three MOSFET elements (104, 106, 108) in the level shift section and an output stage having an NPN transistor (120) in combination with an N-channel MOSFET ( 122).

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First Claim