This paper presents a low power, high linearity wideband cascode low noise amplifier (LNA) targeting the multi-standard wireless communication applications including LTE, GSM and Zigbee. Analyzing a cascode amplifier shows the common source (CS) stage is the main nonlinearity source for the LNA. The modified derivative superposition (MDS) technology is widely adopted to improve the linearity. In addition, when the operating frequency increases, the nonlinearity influence coming from the common gate (CG) increases and limits the linearity performance of the LNA. Based on the modified derivative superposition (MDS) technique, this work investigates the nonlinearity effects of the common gate (CG) stage on the cascode amplifier and employs both the derivative superposition (DS) and a terminal LC resonator on the CG stage. The nonlinearity coming from the CG stage is degraded in higher frequency and the high linear bandwidth is also increased. A cascode LNA was designed, analyzed, and implemented in the IBM 0.13-μm CMOS technology. The LNA achieved a third-order intercept point (IIP3) of +13.6 dBm, 3 dB NF and a 12 dB gain in a wide frequency from 700 MHz to 1.1 GHz.
In this paper, an input inductive network for the wideband LNA is proposed. The two input inductors located in and out of the feedback loop are set respectively to combine with the conventional resistive feedback structure. Input matching and NF of the LNA can be optimized separately by varying the value of the two input inductors without significant influence from one to the other. The proposed cascode LNA was analyzed, designed, and fabricated in the IBM 0.13 μm CMOS technology to verify the concept. A À10 dB S11 is achieved in a wide range of frequency from 1 GHz to 3 GHz. Within this bandwidth, the LNA has a gain of 7.5 dB and a minimum noise figure of 2.5 dB while consumes a 7 mW of power. The results indicate that the proposed input-network effectively alleviates the tradeoff between noise figure and bandwidth without requiring extra power consumption.
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