Variable-gain differential amplifier
AssigneeSTMicroelectronics S.r.l.
InventorPaolo Gatti
Life of this patent
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Abstract
A variable-gain amplifier with high input impedance includes positive and negative inputs, positive and negative outputs, first and second differential circuits and first, second and third impedances. The impedances form an impedance bridge between the outputs. The first and second differential circuits each have one input coupled to one of the inputs of the differential amplifier, one input coupled to the impedance bridge, and two outputs connected to the outputs of the differential amplifier. At least one of the impedances is a variable impedance.
Claims20
A differential amplifier having a first input, a second input, a first output and a second output, comprising:
- a first differential circuit having a first input coupled to the first input of the differential amplifier, a second input, and first and second outputs respectively coupled to the first and second outputs of the differential amplifier;
- a second differential circuit having a first input coupled to the second input of the differential amplifier, a second input, and first and second outputs respectively coupled to the second and first outputs of the differential amplifier;
- a first impedance coupling the first output of the differential amplifier to the second input of the first differential circuit;
- a second impedance coupling the second output of the differential amplifier to the second input of the second differential circuit;
- and
- a third impedance coupling the second input of the second differential circuit to the second input of the first differential circuit,
- wherein at least one of the first, second and third impedances is a variable impedance, and
- wherein the first and second inputs of each of the first and second differential circuits correspond to the respective gates of a differential pair of transistors of the circuits.
A differential amplifier having a first input, a second input, a first output and a second output, comprising:
- a first differential circuit having a first input coupled to the first input of the differential amplifier, a second input, and first and second outputs respectively coupled to the first and second outputs of the differential amplifier;
- a second differential circuit having a first input coupled to the second input of the differential amplifier, a second input, and first and second outputs respectively coupled to the second and first outputs of the differential amplifier;
- a first switched resistor array coupling the first output of the differential amplifier to the second input of the first differential circuit;
- a second switched resistor array coupling the second output of the differential amplifier to the second input of the second differential circuit;
- and
- a fixed impedance coupling the second input of the second differential circuit to the second input of the first differential circuit.
Dependencies are inferred from the claim text.