Amplifier with bias compensation using a current mirror circuit
First Claim
1. An amplifier circuit comprising:
- an amplifying transistor;
a dc bias circuit comprising;
a first transistor forming a current mirror with said amplifying transistor with their bases coupled at a first common node and their emitters coupled to a common terminal;
a second transistor having an emitter coupled to said first common node and a base coupled to a collector of said first transistor at a second common node;
a bias power source coupled to said second common node through a resistor and an inductor connected in series at a third common node, and directly coupled to a collector of said second transistor as well;
wherein said dc bias circuit further comprises a bypass capacitor coupled between said third common node and a ground.
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Accused Products
Abstract
A power amplifier circuit comprises an amplifying transistor and a dc bias circuit. The dc bias circuit comprises a first transistor in a current mirror with the amplifying transistor, and a second transistor to provide the base currents to both the amplifying transistor and the first transistor. A dc bias power source is coupled to the base of the second transistor through a resistor and an inductor connected in series. A bypass capacitor is coupled between a ground and a node between the resistor and the inductor. Thus, the reduced voltage drop across the base-emitter junction of the amplifying transistor due to an increased input power is compensated. Furthermore, by properly scaling the emitter area ratio between the amplifying transistor and the first transistor, and/or the ratio between a bias resistor and a corresponding resistor coupled with the mirroring first transistor, the quiescent current in the amplifying transistor can be made to be in direct proportion to that of the first transistor.
19 Citations
17 Claims
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1. An amplifier circuit comprising:
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an amplifying transistor;
a dc bias circuit comprising;
a first transistor forming a current mirror with said amplifying transistor with their bases coupled at a first common node and their emitters coupled to a common terminal;
a second transistor having an emitter coupled to said first common node and a base coupled to a collector of said first transistor at a second common node;
a bias power source coupled to said second common node through a resistor and an inductor connected in series at a third common node, and directly coupled to a collector of said second transistor as well;
wherein said dc bias circuit further comprises a bypass capacitor coupled between said third common node and a ground. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A power amplifier circuit, comprising:
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an amplifying transistor;
a dc bias circuit having a first transistor forming a current mirror with said amplifying transistor while a second transistor providing base currents for both of said amplifying transistor and said first transistor, a dc bias power source coupled directly to a collector of said second transistor and coupled to a base of said second transistor through a resistor and an inductor connected in series, wherein a bypass capacitor is coupled in parallel to said resistor. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification