Device for balancing the rise and fall slew-rates of an operational amplifier
AssigneeSTMicroelectronics (Grenoble 2) SAS
InventorsPhilippe Maige, Pawel Fiedorow
Life of this patent
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Abstract
An amplifier includes a pair of transistors connected in a differential stage, and a bias current source connected to a common node of the differential stage. A slew-rate compensation circuit is configured to derive from the common node a dynamic compensation current during a phase in which the voltage of the common node varies.
Claims10
An amplifier comprising:
- a pair of transistors coupled in a differential stage including a common node;
- a bias current source coupled to the common node of the differential stage;
- and
- a slew-rate compensation circuit configured to derive from the common node a dynamic compensation current during a phase in which a voltage of the common node varies, the slew-rate compensation circuit comprising
- a capacitor configured to replicate voltage variations of the common node on the capacitor and to generate the dynamic compensation current from a current flowing in the capacitor,
- a follower transistor having a control terminal coupled to a control terminal of a first transistor of the differential pair and a first conduction terminal coupled to a terminal of the capacitor, and
- a current mirror having an input coupled to the second conduction terminal of the follower transistor and an output coupled to the common node.
An amplifier comprising:
- a pair of transistors coupled at a common node;
- a bias current source coupled to the common node;
- a capacitor configured to replicate voltage variations of the common node on the capacitor and to generate a compensation current from a current flowing in the capacitor;
- a follower transistor having a control terminal coupled to a control terminal of a first transistor of the pair and a first conduction terminal coupled to the capacitor;
- and
- a current mirror having an input coupled to a second conduction terminal of the follower transistor and an output coupled to the common node.
A method of making an amplifier, the method comprising:
- coupling a pair of transistors in a differential stage at a common node;
- coupling a bias current source to the common node of the differential stage;
- and
- coupling a slew-rate compensation circuit to the common node to generate a dynamic compensation current during a phase in which a voltage of the common node varies, the slew rate compensation circuit comprising a capacitor, a follower transistor having a control terminal coupled to a control terminal of a first transistor of the pair and a first conduction terminal coupled to the capacitor, and a current mirror having an input coupled to a second conduction terminal of the follower transistor and an output coupled to the common node.
A method of operating an amplifier comprising a pair of transistors coupled in a differential stage at a common node, a bias current source coupled to the common node of the differential stage, and a slew rate compensation circuit comprising a capacitor, a follower transistor having a control terminal coupled to a control terminal of a first transistor of the pair and a first conduction terminal coupled to the capacitor, and a current mirror having an input coupled to a second conduction terminal of the follower transistor and an output coupled to the common node, the method comprising:
- balancing slew rates in the amplifier by generating a dynamic compensation current during a phase in which a voltage of the common node varies using the slew rate compensation circuit.
Dependencies are inferred from the claim text.