Power amplifier with bias control
First Claim
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1. A power amplifier comprising:
- a first stage including a signal amplification transistor for amplifying an input signal, the signal amplification transistor having a control electrode responsive to a bias current, anda first bias circuit including a controlled current source for converting a gain control voltage to the bias current, wherein the bias circuit includes a non-linear voltage/current converter for converting the gain control voltage to the bias current.
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Abstract
A power amplifier (100) suitable for use in mobile telecommunications equipment has a first stage (2) and an optional second stage (2), each stage being provided with a bias circuit (4, 5). To provide a well-defined gain characteristic, in the first stage (1) a bias current (Ib1) is fed into a signal amplifying transistor (T1). The first bias circuit (4) comprises non-linear a voltage/current converter (41) coupled to a current mirror (40). To suit alternative applications, such as GSM and UMTS requiring a different bias, plural voltage/current converters (41, 42) may be provided in parallel.
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Citations
9 Claims
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1. A power amplifier comprising:
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a first stage including a signal amplification transistor for amplifying an input signal, the signal amplification transistor having a control electrode responsive to a bias current, and a first bias circuit including a controlled current source for converting a gain control voltage to the bias current, wherein the bias circuit includes a non-linear voltage/current converter for converting the gain control voltage to the bias current. - View Dependent Claims (2, 3, 5, 7, 8, 9)
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4. A power amplifier comprising:
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a first stage for amplifying an input signal, and a first bias circuit for providing a bias current to the first stage, the first bias circuit including a controlled current source, and the first bias circuit being arranged for feeding its bias current to a control electrode of a signal amplification transistor of the first stage, wherein at least one bias circuit comprises two distinct voltage/current converters for converting two distinct gain control voltages.
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6. A power amplifier comprising:
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a first stage for amplifying an input signal, and a first bias circuit for providing a bias current to the first stage, the first bias circuit including a controlled current source and a voltage/current converter, and the first bias circuit being arranged for feeding its bias current to a control electrode of a signal amplification transistor of the first stage, wherein in the first bias circuit an additional transistor is coupled between the voltage/current converter and the controlled current source so as to compensate for a DC current gain of the signal amplification transistor.
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Specification