Amplifying circuit and method for improving linearity by using grid non-linear capacitor

Abstract

An amplifying device is used for amplifying an input signal which corresponds to an operation frequency. The device comprises a first amplifying circuit and a first resonance circuit; the first amplifying circuit is used for amplifying the input signal, so as to produce a first output signal; the first amplifying circuit comprises a first input transistor; the first input grid end of the first input transistor is used for receiving the input signal; the first resonance circuit is coupled with the first input grid end; and first resonance frequency of the first resonance circuit is not equal to the preset operation frequency.

Description

technical field [0001] The invention relates to a power amplifying circuit, in particular to a power amplifying circuit and a method for improving linearity. Background technique [0002] The application scope of power amplifier is more and more extensive. Generally speaking, the factors that affect the performance of the amplifier include the size of the maximum power gain and the quality of the linearity. The quality of the linearity is the comparison of the degree of distortion between the input power and the output power. In addition, due to the advancement of CMOS process technology and the advent of the system-on-chip (SOC) era, the use of CMOS process to manufacture full-chip wireless transmitters has become a topic of current RF circuit design. Please refer to known techniques C.Wang, M.Vaidyanathan, and L.E.Larson, "A Capacitance Compensation Technique for ImprovedLinearity in CMOS Class-AB Power amplifiers," IEEE-J.Solid-State-Circuits, vol.39, no.11 , pp.1927-19...

AI Technical Summary

Problems solved by technology

Generally speaking, the nonlinear sources of CMOS power amplifiers are mainly divided into two parts, one is the transconductance (transconductance, Gm) of the transistor itself, which determines the linearity of the transistor itself, and the other is the gate terminal of the transistor. The nonlinear capacitance C gate , which is the output load of the previous stage circuit, so it determines the linearity of the signal at the output terminal of the previous stage circuit. In the above-mentioned known technology, a capacitance compensation method has been proposed to improve the nonlinear capacitance C of the gate terminal of the transistor gate The non-linear effect caused, but only applicable to the CMOS power amplifier of AB level (Class-AB) structure in the above-mentioned known technology, and it will influence power gain and need bigger chip area

However, for Orthogonal Frequency Division Multiplexing (OFDM) systems that require very high linearity (for example, the linearity requirement of the 802.11g specification requires P1dB to be 25dBm), only Class A (Class A) power amplifiers become a more achievable architecture. Class A power amplifiers are also often affected by the above-mentioned nonlinear capacitance, making their linearity worse.

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