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US 7,256,648 B2Granted
Variable feedback circuits and methods
AssigneePacificTech Microelectronics, Inc.
InventorsHideto Takagishi, Simon Tsai
Life of this patent
Estimating the term…
Abstract
In one embodiment, the present invention includes a circuit comprising an amplifier having an input terminal, an output terminal, a positive supply voltage, and a negative supply voltage. The amplifier is configured to have a first gain. A variable feedback circuit is coupled between the input terminal and the output terminal. The difference between the voltage on the output terminal and input terminal is received by the variable feedback circuit, which changes the gain of the circuit and reduces distortion.
Claims18
A circuit comprising:
- an amplifier having an input terminal, an output terminal, a positive supply voltage, and a negative supply voltage, the amplifier configured to have a first gain;
- and
- a variable feedback circuit coupled between the input terminal and the output terminal,
- wherein if the difference between the voltage on the output terminal and the positive supply voltage is less than a predetermined value, then the variable feedback circuit reconfigures the amplifier to have a second gain less than the first gain, and if the difference between the voltage on the output terminal and the negative supply voltage is less than a predetermined value, then the variable feedback circuit reconfigures the amplifier to have a third gain less than the first gain.
1 more element
A circuit comprising:
- an amplifier having a first and second input terminals, an output terminal, a positive supply voltage, and a negative supply voltage;
- a first resistor coupled between the output terminal and the first input terminal;
- a first transistor having a first terminal, a second terminal, and a control terminal, wherein the first terminal of the first transistor is coupled to the outPut terminal of the amplifier and the control terminal is coupled to a first reference voltage;
- and
- a second resistor coupled between the second terminal of the first transistor and the first input terminal of the amplifier, wherein the first reference voltage is configured so that the first transistor conducts current between the output terminal of the amplifier and the second resistor when the difference between the voltage on the output terminal of the amplifier and the voltage on the input terminal of the amplifier is positive and greater than a predetermined value.
2 more elements
A circuit comprising:
- an amplifier having a first and second input terminals, an output terminal, a positive supply voltage, and a negative supply voltage;
- a first resistor coupled between the output terminal and the first input terminal;
- a first transistor having a first terminal a second terminal, and a control terminal, wherein the first terminal of the first transistor is coupled to the output terminal of the amplifier and the control terminal is coupled to a first reference voltage;
- a second resistor coupled between the second terminal of the first transistor and the first input terminal of the amplifier;
- and
- a second transistor having a first terminal, a second terminal, and a control terminal, wherein the first terminal of the second transistor is coupled to the output terminal of the amplifier, the control terminal of the second transistor is coupled to a second reference voltage, and the second terminal of the second transistor is coupled to the second resistor, wherein the second reference voltage is configured so that the second transistor conducts current between the output terminal of the amplifier and the second resistor when the difference between the voltage on the output terminal of the amplifier and the voltage on the input terminal of the amplifier is negative and greater than a predetermined value.
3 more elements
A circuit comprising:
- an amplifier having an first and second input terminals, an output terminal, a positive supply voltage, and a negative supply voltage;
- a first resistor coupled between the output terminal and the first input terminal;
- a first transistor having a first terminal, a second terminal, and a control terminal, wherein the first terminal of the first transistor is coupled to the output terminal of the amplifier and the control terminal is coupled to a first reference voltage;
- a second resistor coupled between the second terminal of the first transistor and the first input terminal of the amplifier;
- and
- at least three resistors coupled in series between a positive supply voltage and a negative supply voltage, wherein a first intermittent node between a first two of said at least three resistors is coupled to the control terminal of the first transistor, and wherein a second intermittent node between a second two of said at least three resistors is coupled to the control terminal of the second transistor.
3 more elements
An amplifier method comprising:
- configuring said amplifier in a first gain;
- and
- reconfiguring said amplifier to have a second gain less than the first gain if the difference between the voltage on an output terminal of said amplifier and a positive supply voltage for said amplifier is less than a first predetermined value or if the difference between the voltage on the output terminal of said amplifier and a negative supply voltage is less than a second predetermined value.
Dependencies are inferred from the claim text.