Operational amplifier output stage and method
First Claim
1. An amplifier comprising:
- (a) an input stage for producing a first voltage signal;
(b) an output stage for producing an output signal in response to the first voltage signal, the output stage includingi. a first output transistor having a first electrode coupled to a first supply rail and a control electrode coupled to receive the first voltage signal,ii. a first output cascode transistor having a first electrode coupled to a second electrode of the first output transistor and a second electrode coupled to an output conductor conducting the output signal, andiii. a first gate control amplifier including a first input stage including a first input transistor having a control electrode coupled to the first electrode of the first output cascode transistor and a first active load transistor, the first input transistor and the first active load transistor being coupled to a first output coupled to a control electrode of the first output cascode transistor, the first gate control amplifier also including a first ancillary stage having an input coupled to the first electrode of the first output cascode transistor and an output coupled to a control electrode of the first active load transistor.
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Accused Products
Abstract
An operational amplifier includes an input stage for producing a voltage signal in response to an input signal. An output stage includes an output transistor having a source coupled to a supply voltage and a gate coupled to receive the voltage signal. An output cascode transistor has a source coupled to a drain of the output transistor and a drain coupled to an output conductor. A gate control amplifier includes an input stage including a first input transistor having a control electrode coupled to the source of the output cascode transistor and an active load transistor, the input transistor and the active load transistor being coupled to a gate of the output cascode transistor. The gate control amplifier also includes a feedback amplifier having an input coupled to the source of the output cascode transistor and an output coupled to a control electrode of the active load transistor.
23 Citations
20 Claims
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1. An amplifier comprising:
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(a) an input stage for producing a first voltage signal; (b) an output stage for producing an output signal in response to the first voltage signal, the output stage including i. a first output transistor having a first electrode coupled to a first supply rail and a control electrode coupled to receive the first voltage signal, ii. a first output cascode transistor having a first electrode coupled to a second electrode of the first output transistor and a second electrode coupled to an output conductor conducting the output signal, and iii. a first gate control amplifier including a first input stage including a first input transistor having a control electrode coupled to the first electrode of the first output cascode transistor and a first active load transistor, the first input transistor and the first active load transistor being coupled to a first output coupled to a control electrode of the first output cascode transistor, the first gate control amplifier also including a first ancillary stage having an input coupled to the first electrode of the first output cascode transistor and an output coupled to a control electrode of the first active load transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of operating an amplifier output stage to reduce power dissipation during peak output currents, the method comprising:
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(a) providing a first output transistor having a first electrode coupled to a first supply rail and a control electrode coupled to receive a first voltage signal and a first output cascode transistor having a first electrode coupled to a second electrode of the first output transistor and a second electrode coupled to an output conductor conducting an output signal; (b) controlling a voltage on a control electrode of the first output cascode transistor in response to a first control signal on a first electrode of the first output cascode transistor by applying the first control signal to a control electrode of a first input transistor of an input stage of a first control amplifier, the input stage of the first control amplifier including an active load transistor, a second electrode of the first input transistor of the input stage of the first control amplifier being coupled to a first electrode of the active load transistor of the input stage of the first control amplifier; and (c) controlling a voltage on a control electrode of the active load transistor of the input stage of the first control amplifier in response to the first control signal in accordance with a current produced in the first output transistor in response to the first voltage signal. - View Dependent Claims (16, 17, 18, 19)
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20. An amplifier output stage having reduced power dissipation during peak output currents, comprising:
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(a) a first output transistor having a first electrode coupled to a first supply rail and a control electrode coupled to receive a first voltage signal and a first output cascode transistor having a first electrode coupled to a second electrode of the first output transistor and a second electrode coupled to an output conductor conducting an output signal; and (b) circuitry for controlling a voltage on a control electrode of the first output cascode transistor in response to a control signal on a first electrode of the first output cascode transistor, the control circuitry including i. means for applying the control signal to a control electrode of an input transistor of an input stage of a control amplifier, and ii. means for controlling an active load transistor in response to the control signal, a second electrode of the first input transistor being coupled to a first electrode of the active load transistor to boost the magnitude of the voltage on the control electrode of the first output cascode transistor in response to a large current flowing through the first output cascode transistor.
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Specification