Gain block with stable internal bias from low-voltage power supply
First Claim
1. A circuit for biasing a first transistor having a control terminal, current-sink terminal, and current-source terminal and capable of operating at least from a first regulated power supply and a second power supply, the circuit comprising:
- a. a second transistor having a control terminal, current-sink terminal and current-source terminal, wherein the control terminal of the second transistor is connected to the control terminal of the first transistor in a current-mirror configuration, and wherein the current-source terminal of the second transistor is connected to a first terminal of the first regulated power supply;
b. at least one resistor connected between the current-sink terminal of the second transistor and a second terminal of the first regulated power supply;
c. a feedback circuit, including a non-inverting amplifier having a feedback transistor, and input and output ports, wherein the input port of the non-inverting amplifier is connected to the at least one resistor and the current-sink terminal of the second transistor; and
wherein furthermore a control terminal of a feedback transistor is connected to the output port of the non-inverting amplifier, and a current-source terminal of the feedback transistor connected to the second transistor and the first transistor, with the current-sink terminal of the feedback transistor connected to the second terminal of the second power supply, whereby the non-inverting amplifier increases the gain of the feedback circuit so that the bias circuit is relatively insensitive to fluctuations in supply voltage or temperature.
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Accused Products
Abstract
A transistor bias circuit is provided that is capable of operating from a power supply voltage that is slightly higher than twice the base-emitter voltage of the transistor to be biased. The bias circuit includes a transistor connected in a current-mirror configuration with the transistor to be biased. A feedback circuit maintains the mirrored current at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit. In a preferred embodiment, the biased transistor is concurrently in both a Darlington and the current mirror configuration. Moreover, a feedback transistor in the feedback circuit is also concurrently in the Darlington configuration, thus providing an efficient biasing arrangement for an amplifier block based on the Darlington arrangement.
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Citations
21 Claims
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1. A circuit for biasing a first transistor having a control terminal, current-sink terminal, and current-source terminal and capable of operating at least from a first regulated power supply and a second power supply, the circuit comprising:
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a. a second transistor having a control terminal, current-sink terminal and current-source terminal, wherein the control terminal of the second transistor is connected to the control terminal of the first transistor in a current-mirror configuration, and wherein the current-source terminal of the second transistor is connected to a first terminal of the first regulated power supply;
b. at least one resistor connected between the current-sink terminal of the second transistor and a second terminal of the first regulated power supply;
c. a feedback circuit, including a non-inverting amplifier having a feedback transistor, and input and output ports, wherein the input port of the non-inverting amplifier is connected to the at least one resistor and the current-sink terminal of the second transistor; and
wherein furthermore a control terminal of a feedback transistor is connected to the output port of the non-inverting amplifier, and a current-source terminal of the feedback transistor connected to the second transistor and the first transistor, with the current-sink terminal of the feedback transistor connected to the second terminal of the second power supply,whereby the non-inverting amplifier increases the gain of the feedback circuit so that the bias circuit is relatively insensitive to fluctuations in supply voltage or temperature. - View Dependent Claims (2, 3, 4, 5)
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6. A method of biasing a first transistor having a control terminal, a current-sink terminal, and a current-source terminal and capable of operating from a power supply having positive and ground terminals via a bias circuit including a second transistor connected in a current-mirror configuration with the first transistor, the method comprising the steps of:
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a. monitoring an electrical characteristic at the current-sink terminal of the second transistor;
b. amplifying the monitored characteristic; and
c. feeding back the amplified characteristic to control the second transistor. - View Dependent Claims (7, 8, 9)
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10. A circuit for biasing one or more transistors, the circuit comprising:
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a regulated low voltage supply terminal providing a reference current to a first transistor in a current mirror configuration;
an amplifier providing feedback to counteract variations;
a Darlington arrangement comprising a second transistor concurrently in the current mirror configuration;
an input coupled to at least one transistor in the Darlington arrangement;
an output terminal; and
a power supply connected to the second transistor and providing a biasing current to the Darlington arrangement in accordance with a mirror current to the second transistor in the current mirror configuration. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A method of biasing an amplification stage having a Darlington configuration with a biasing network having reduced power consumption, the method comprising:
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providing a reference current to a master transistor from a regulated supply; and
providing a biasing current from another supply to one of the transistors in the Darlington arrangement such that the one of the transistors is in a current mirror configuration with the master transistor.
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18. A method for designing a circuit for biasing a Darlington arrangement, the method comprising:
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providing a reference current through a master transistor;
providing a mirror current substantially related to the reference current by a scaling factor through a first transistor in the Darlington arrangement; and
providing a biasing current through a second transistor coupled to the first transistor in the Darlington arrangement. - View Dependent Claims (19)
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20. A circuit for biasing a plurality of transistors, the circuit comprising:
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a regulated low voltage supply terminal providing a reference current to a first transistor in a current mirror configuration;
an amplifier providing feedback to counteract variations;
a cascade arrangement of transistors comprising a second transistor concurrently in the current mirror configuration;
an input coupled to at least one transistor in the cascade arrangement of transistors; and
an output terminal connected to a power supply providing a biasing current to the cascade arrangement of transistors in accordance with a mirror current to the second transistor in the current mirror configuration. - View Dependent Claims (21)
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Specification