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US 4,375,619 AGranted
FET Operational amplifier with increased output swing
AssigneeBell Telephone Laboratories, Incorporated
InventorVeikko R. Saari
Life of this patent
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AssigneeBell Telephone Laboratories, Incorporated
InventorVeikko R. Saari
Estimating the term…
A differential input stage is connected to a push-pull output stage with a complementary MOS output pair (30, 32) in a common-source configuration. The gates of the output transistors (30, 32) are each driven by the output of one of a pair of auxiliary transistors (38, 42) which have their gates coupled to the signal. A separate bias current source (41, 44) is connected between the output of each of the auxiliary transistors and a supply node (26). The bias current sources (41, 44) draw current in proportion to the ratio of the transconductances of the auxiliary drive transistors (42, 38) for establishing the voltage across a coupling resistor (36) connecting the output transistor (30, 32) gates and thereby determining the crossover current of the output stage (50). Also disclosed is a frequency response compensation network circuit section (74) which is phase-inverting and provides a local negative feedback loop for the tandem arrangement of intermediate stage (48) and the output stage (50).
An operational amplifier having first and second power supply nodes for supplying power to first and second stages, said first stage having first and second output nodes coupled to said second stage, said second stage comprising a complementary pair of first and second field effect transistors connected in series between said supply nodes with their drain terminals connected together at an output node of said second stage and their gates connected together through a first resistor, said amplifier being characterized by:
Dependencies are inferred from the claim text.