Compensated gain-controlled amplifier having a wide linear dynamic range
First Claim
1. An amplifier circuit for amplifying a received signal, the amplifier circuit comprising:
- a gain setting circuit for generating a gain compensation signal which remains constant as a function of temperature;
a temperature sensing circuit for generating a temperature compensation signal which remains constant as a function of said gain compensation signal, anda dual gate field effect transistor circuit having a first gate coupled to said temperature sensing circuit and coupled to said receive signal and a second gate coupled to said gain setting circuit, the field effect transistor generating an amplified signal from the received signal in response to the temperature compensation signal and the gain compensation signal.
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Abstract
A high dynamic range linear automatic gain control (AGC) circuit that has independent means for temperature compensation. The temperature compensation circuit of this invention can be used in a closed-loop AGC circuit such as is required in a transceiver for compensating the gains of receiver and transmitter amplifiers to ensure that both track closely over ranges of temperature, frequency and load impedance. The temperature compensation signal is coupled to one of the two gates in a field effect transistor (FET) amplifier to maintain a constant gain function over ranges of temperature, frequency and load impedance. Thermal compensation for the transmitter amplifier is derived from the thermal compensation signal for the receiver amplifier.
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Citations
12 Claims
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1. An amplifier circuit for amplifying a received signal, the amplifier circuit comprising:
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a gain setting circuit for generating a gain compensation signal which remains constant as a function of temperature; a temperature sensing circuit for generating a temperature compensation signal which remains constant as a function of said gain compensation signal, and a dual gate field effect transistor circuit having a first gate coupled to said temperature sensing circuit and coupled to said receive signal and a second gate coupled to said gain setting circuit, the field effect transistor generating an amplified signal from the received signal in response to the temperature compensation signal and the gain compensation signal.
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2. An amplifier circuit providing temperature independent gain to a modulated signal comprising:
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a gain control circuit generating independent of a current temperature a gain control signal indicative of a desired level of gain; a temperature control circuit generating a temperature compensation signal indicative of said current temperature wherein said temperature compensation signal is independent of said desired level of gain; and a dual gate field effect transistor circuit having a first gate receiving said temperature compensation signal and said modulated signal and a second gate receiving said gain control signal, said dual gate field effect transistor having a drain producing an amplified version of said modulated signal having an amplification dependent on the value of said gain control signal and independent of said current temperature. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification