Active circuit having a temperature stable bias
AssigneeMotorola, Inc.
InventorsDavid H. Minasi, Peter J. Yeh, Roger A. Davenport, Gustavo V. Leizerovich
Life of this patent
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Abstract
An active circuit includes an amplifying transistor (102), a voltage reference (208), and an active bias circuit. The active bias circuit controls the operating point of the amplifying transistor, and includes a bias transistor (224) which is controlled by the voltage reference and the collector current of the amplifying transistor. As the temperature of the amplifying transistor changes, the tendency of the collector current to change is counter-acted by the bias transistor and the voltage reference.
Claims19
An active circuit having a temperature stable bias, comprising:
- an amplifying transistor having a collector, an emitter, a base, and a collector current;
- a voltage reference having a temperature coefficient;
- and
- a bias transistor connected between the collector and the base of the amplifying transistor, and responsive to the voltage reference, the bias transistor having a temperature coefficient substantially equal to the temperature coefficient of the voltage reference, the bias transistor providing a bias current to the amplifying transistor such that the collector current is held substantially constant over a predetermined temperature range.
An active circuit connected between an upper voltage potential and a lower voltage potential, and having a temperature stable bias, the active circuit comprising:
- an amplifying transistor having a collector, an emitter, a base, and a collector current;
- a reference node for providing a stable voltage level;
- a reference transistor connected in a diode configuration between the reference node and a pull down resistor, the reference transistor providing a reference voltage;
- a bias transistor connected between the collector and the base of the amplifying transistor, and responsive to the reference voltage such that the collector current of the amplifying transistor is held substantially constant over a predetermined temperature range;
- and
- a current sense resistor connected between the collector of the amplifying transistor and the upper voltage potential.
An active circuit connected between an upper voltage potential and a lower voltage potential, comprising:
- an amplifying transistor having a collector, an emitter, a base, and a collector current, a current sense resistor connected between the upper voltage potential and the collector;
- a voltage divider connected between the upper voltage potential and the lower voltage potential, and providing a reference node;
- a reference transistor connected in a diode configuration between the reference node and a pull down resistor, the reference transistor providing a reference voltage across the pull down resistor;
- and
- a bias transistor having a first terminal connected to the collector of the amplifying transistor, a second terminal connected to the pull down resistor and the reference transistor, and a third terminal connected to the base of the amplifying transistor through a bias resistor.
Dependencies are inferred from the claim text.