Precision operational amplifier with a floating input stage
AssigneeSemiconductor Components Industries, LLC
InventorCatalin Ionut Petroianu
Life of this patent
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Abstract
The operational amplifier disclosed includes an input stage configured to receive power from a floating supply in a low voltage range that can float according to the common mode voltage at the input. The floating supply facilitates the use of low voltage components that can improve the precision of the operational amplifier by lowering the offset voltage. The input stage includes a first gain stage including field effect transistors and a second gain stage using bipolar transistors. The gain stages can be implemented differently to accommodate different applications and fabrication capabilities.
Claims20
An input stage for an operational amplifier, the input stage comprising:
- a first gain stage including:
- a first field effect transistor coupled at a first gate to a positive input of the operational amplifier;
- and
- a second field effect transistor coupled at a second gate to a negative input of the operational amplifier;
- and
- a second gain stage including:
- a first bipolar transistor coupled at a first emitter to a negative output of the first gain stage and coupled at a first collector to a negative output of the input stage;
- a second bipolar transistor coupled at a second emitter to a positive output of the first gain stage and coupled at a second collector to a positive output of the input stage;
- and
- an active load coupled to the first collector and the second collector, the active load including a pair of bipolar transistors and a pair of resistors coupled to respective emitters of the pair of bipolar transistors.
An operational amplifier including:
- an input stage including:
- a first differential pair including field effect transistors source terminals connected together at a common source node of the input stage, a voltage at the common source node corresponding to an input voltage of the operational amplifier;
- a pair of resistors coupled between drain terminals of the first differential pair of field effect transistors, the pair of resistors connected together at a floating node of the input stage;
- and
- a second different pair including bipolar transistors coupled at emitter terminals to the pair of resistors and connected together at a common base node of the input stage;
- and
- a floating supply configured to receive the voltage at the common source node and generate a relative voltage at the floating node.
Dependencies are inferred from the claim text.