WIDEBAND LOW NOISE AMPLIFIERS |
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申请号 | US12030808 | 申请日 | 2008-02-13 | 公开(公告)号 | US20090121791A1 | 公开(公告)日 | 2009-05-14 |
申请人 | Shey-Shi LU; Hsien-Ku CHEN; | 发明人 | Shey-Shi LU; Hsien-Ku CHEN; | ||||
摘要 | A wideband low noise amplifier. The wideband low noise amplifier comprises an amplifier, an output device, and an inductor. The amplifier amplifies an input signal received from an input node, and outputs the amplified signal to an output node. The output device is coupled to a first voltage and the output node. The peaking inductor is coupled between the amplifier and the output device. | ||||||
权利要求 | What is claimed is: |
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说明书全文 | 1. Field of the Invention The invention relates to a wideband low noise amplifier, and more particularly to an ultra-wideband (UWB) low noise amplifier. 2. Description of the Related Art Recently, wideband systems with high frequency transmission capabilities have become more and more popular. For example, ultra-wideband (UWB) system using 3.1 GHz to 10.6 GHz transmission bands offering faster speed and wireless transmission capabilities. Along with development of wideband technology, the bandwidth of the elements adopted in the wideband systems must also be extended. For example, a low noise amplifier (LNA) disposed between an antenna and pre-select filter in the UWB system requires a 50 input resistance and 3.1 GHz to 10.6 GHz bandwidth design. Thus, an improved wideband low noise amplifier with low power consumption, wideband resistance match and a small chip area for a UWB system is required. Wideband low noise amplifiers are provided. An exemplary embodiment of such a wideband low noise amplifier comprises an amplifier, an output device and a peaking inductor. The amplifier amplifies an input signal received from a signal input terminal, and outputs an amplified signal to a signal output terminal. The output device is coupled to a first power supply and the signal output terminal. The peaking inductor is coupled between the amplifier and the output device. An exemplary embodiment of a wideband low noise amplifier for amplifying an input signal received from a signal input terminal and outputting an amplified signal to a signal output terminal comprises a first transistor, a transmission line, an output device, a first resistor, a second transistor and a first inductor. The first transistor comprises a gate coupled to the signal input terminal. The transmission line is coupled between a source of the first transistor and a ground node. The output device is coupled to a first power supply and the signal output terminal. The first resistor is coupled between the gate of the first transistor and the output device. The second transistor comprises a gate coupled to a second power supply, and a source coupled to a drain of the first transistor. The first inductor is coupled between a drain of the second transistor and a first connection node of the first resistor and the output device. A detailed description is given in the following embodiments with reference to the accompanying drawings. The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. Because resonant circuit with capacitor and inductor connected in serial is used at the input terminal of the amplifier 41, the amplifier 41 obtains higher quality factor. Higher quality factor makes the frequency response of the reflection factor S11 act like a narrow band bandpass filter, which restrains the bandwidth of amplifier 41. Furthermore, the parasitism capacitor Cgs, Cgd, Cdb, and Csb of transistors M1 and M2 are also factors that restrain the bandwidth of amplifier 41. Thus, according to one embodiment of the invention, a feedback resistor R1 is used to decrease the quality factor of amplifier 41. According to the embodiment of the invention, the resistance of the feedback resistor R1 can be chosen between 100Ω-500Ω, wherein when the resistance of the feedback resistor R1 is 300Ω, the frequency response of the reflection factor S11 of the wideband low noise amplifier 40 is more preferable. Furthermore, in order to increase the power gain of the amplifier 41 at high frequency area, a peaking inductor L1 coupled between the inductor L3 and the drain of transistor M2 is used to extend the bandwidth of the amplifier 41. By using series peaking inductor L1, peaking inductor L1 resonate with the parasitism capacitor Cp at the drain of transistor M2. In this way, the gain of the wideband low noise amplifier 40 is increased at the corresponding resonant frequency. Thus, the bandwidth of the wideband low noise amplifier 40 can be effectively extended by properly selecting the inductance of peaking inductor L1. According to one embodiment of the invention, the inductance of the peaking inductor L1 is preferably between 0.1 nH-1.13 nH. However, the inductance of the peaking inductor L1 can be larger than 1.13 nH according to different circuit requirements. According to the embodiment of the invention, the wideband low noise amplifier 40 can be implement by 1P6M 0.18 μm CMOS technology, and the die area including the testing pad only requires 0.48×0.69 m2. Thus, according to the embodiment of the invention, the wideband low noise amplifier 40 not only has low power consumption, high gain, better input match, but also has wider frequency response and requires smaller a chip area. Thus, both the chip area and the cost of the low noise amplifier can be effectively reduced. While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. Those who are skilled in this technology can still make various alterations and modifications without departing from the scope and spirit of this invention. Therefore, the scope of the present invention shall be defined and protected by the following claims and their equivalents. |