A Low Distortion and Low Noise Differential Amplifier Suitable for 3G LTE Applications Using the Even- and Odd-Mode Impedance Differences of a Bias Circuit

概要

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A low distortion and low noise differential amplifier using the difference between the even- and odd-mode impedances is proposed. In order to realize an amplifier with high OIP3 and low NF characteristics, the impedance of the bias circuit should be low (<300Ω) at the difference frequency and high (>4kΩ) at the carrier frequency. Although the frequency response of the bias circuit impedance can only meet these conditions with difficulty, owing to the 20MHz Tx signal bandwidth for 3G LTE, the proposed amplifier can achieve the impedance difference using the properties of a differential configuration where the difference frequency signal is the even-mode and the carrier frequency is the odd-mode. It has been demonstrated that the NF of the proposed amplifier, which has been fabricated in 0.18μm SiGe BiCMOS technology operating at 2.14GHz, can be kept to 1.6dB or less and an OIP3 of 9.0dBm can be achieved, which is 3dB higher than that of a conventional amplifier, in the condition where the power gain is greater than 18dB.
（社）電子情報通信学会の論文
2008-06-01