US 6,417,733 B1Granted

High output voltage swing class AB operational amplifier output stage

AssigneeTexas Instruments Incorporated

InventorsMarco Corsi, Priscilla Escobar-Bowser

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Abstract

An output stage (10) is provided having transistors of the same polarity type, which function to amplify the input signal at a wide range of frequencies, with low power consumption and low crossover distortion. By biasing the output transistors to remain on during both the positive and negative voltage swing of the input signal, low power consumption as well as low output crossover distortion is achieved. A high efficiency, low crossover distortion, current amplifier circuit for amplifying an input signal (VIN) in accordance with this present invention includes an output driver (12), a current source (IS1) and a translinear loop circuit (14). The output driver (12) includes a sourcing circuit (Q6). The current source (IS1), connected to the output driver (12), provides bias current to the sourcing circuit. The translinear loop circuit (14), connected to the output driver (12), receives the input signal (VIN). The translinear loop (14) includes a sinking circuit (Q7), such that the translinear loop circuit (14) is responsive to the a sinking current of the sinking circuit and operable to provide a bias current signal proportional to the sinking current.

Claims6

Dependent claims

A high efficiency, low crossover distortion, current amplifier circuit having an input and output node for amplifying an input signal comprising:

a first current source for providing bias current to a sourcing circuit coupled to a first power supply rail;
an output driver coupled to the first current source and the output node, the output driver including a sourcing circuit;
a first transistor having a collector, base and emitter, the base and collector coupled to the current source;
a resistor coupled between the emitter of the first transistor and the output node;
and
a translinear loop circuit coupled to the input node, the first transistor, and the output driver, the translinear loop circuit comprising,
a sinking circuit having a second transistor including a collector, base and emitter, the translinear loop circuit responsive to a sinking current of the sinking circuit and operable to provide a bias current signal proportional to the sinking current,
a third transistor having a collector, base and emitter, the collector coupled to the first power supply rail, the base coupled to the input node,
a second resistor coupled to the emitter of the third transistor,
a fourth transistor having a collector, base and emitter, the collector and base coupled to the second resistor, the emitter coupled to a second power supply rail,
a fifth transistor having a collector, base and emitter, the base coupled to the base of the fourth transistor, the emitter coupled to the second power supply rail, the collector coupled to the emitter of the first transistor,
a sixth transistor having a collector, base and emitter, the collector coupled to the first power supply rail, the base coupled to the input node,
a second current source coupled between the emitter of the sixth transistor and the second power supply rail, the second current source coupled to the sourcing circuit, and
wherein the collector of the second transistor of the sinking circuit is coupled to the output node, the base of the second transistor of the sinking circuit is coupled to the second current source, and the emitter of the second transistor of the sinking circuit is coupled to the second power supply rail.

11 more elements

A high efficiency, low crossover distortion, current amplifier circuit having an input and output node comprising:

a first transistor having a base, an emitter and a collector, the collector coupled to a first power supply rail, the base coupled to the input node;
a first resistor coupled to said emitter of said first transistor;
a second transistor having a base, an emitter and a collector, the collector and the base of the second transistor coupled to the resistor, said emitter of the second transistor coupled to a circuit a second power supply rail;
a first current source coupled to the first power supply rail;
a third transistor having a base, an emitter and a collector, the collector and the base of the third transistor coupled to the first current source;
a fourth transistor having a base, an emitter and a collector, the collector coupled to the emitter of the third transistor, the base coupled the base of the second transistor, the emitter coupled to the second power supply rail;
a fifth transistor having a base, an emitter and a collector, the collector coupled to the first power supply rail, the base coupled the input node;
a second current source coupled between the emitter of the fifth transistor and the second power supply rail;
a sixth transistor having a base, an emitter and a collector, the collector coupled to the first power supply rail, the base coupled the first current source, the emitter coupled to the output node;
a second resistor coupled between the emitter of the third transistor and the output node;
and
a seventh transistor having a base, an emitter and a collector, the collector coupled to the output node, the base coupled to the second current source, the emitter coupled to the second power supply rail.

9 more elements

Dependencies are inferred from the claim text.